Demonstrators stand by a burning barricade in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)

BARCELONA, Spain (AP) — The mayor of riot-stricken Barcelona pleaded Saturday for calm after violent protests by Catalan separatists rocked Spain's second largest city for a fifth consecutive night.

"This cannot continue. Barcelona does not deserve it," Mayor Ada Colau told reporters, adding that Friday's violence was the worst so far.

Protesters clashed with police again later on Saturday despite efforts by some citizens to mediate by gathering between the two sides. There was also a skirmish between separatist supporters and police in a square in Spain's capital, Madrid. Authorities are bracing for more protests in the coming days.

Radical separatists have fought with police every night in Barcelona and other Catalan cities following huge peaceful protests by people angered by Monday's Supreme Court verdict that sentenced nine separatist leaders to prison for their roles in a failed 2017 secession attempt.

More than 500,000 people gathered in downtown Barcelona on Friday in a massive show of support for the secession movement that is backed by roughly half of the wealthy northeastern region's 5.5 million voters.

Before night fell, several hundred masked youths had surrounded the headquarters of the National Police and started a street battle that raged into the night in Barcelona, a popular tourist destination.

"The images of organized violence during the night in Barcelona have overshadowed the half a million people who demonstrated in a peaceful and civic manner to show they rejected the verdict," said Catalan interior chief Miquel Buch, who oversees the regional police.

Rioters have burned hundreds of trash bins and hurled gasoline bombs, chunks of pavement, acid, and firecrackers, among other objects, at police. They have used nails to puncture the tires of police vans and fireworks to hit one police helicopter, without doing it serious damage.

Outnumbered officers in riot gear from both Catalonia's regional police and Spain's national police have used batons, rubber and foam bullets, tear gas and water cannon to battle back.

Residents and tourists have run for cover.

"It has been quite scary," said Deepa Khumar, a doctor from Toronto visiting for a medical conference. "This place, it looks like a war zone."

Authorities say over 500 people have been hurt this week, including protesters and police. Eighteen people remained hospitalized, at least one in very serious condition. Police have made over 150 arrests.

Spanish Interior Minister Fernando Grande-Marlaska said that 101 police officers were injured on Friday alone and that 264 police vehicles have been severely damaged in the week's riots.

A small group of supporters of Spanish unity approached the police headquarters that has been the focus of separatists' rage to give officers flowers and gifts on Saturday.

"We feel so anguished," said 54-year-old economist María Jesús Cortés. "There used to be a nice atmosphere here in Barcelona. Everybody with their own ideas, and that was it. We used to live in peace."

Minister Grande-Marlaska asked Catalonia's regional president to explicitly condemn the escalating violence and express his support for law enforcement officials.

"We have gone five days in which there has not been a firm condemnation of violence" by Catalan leader Quim Torra, Grande-Marlaska said.

Torra has called on protesters to respect the non-violent tenets of the separatist movement that has surged over the past decade.

But on Saturday Torra and his vice president, Pere Aragonès, used a televised address mostly to criticize the Supreme Court verdict. Aragonès also insinuated that the national police, which are controlled by Madrid, had acted too aggressively with protesters.

Torra demanded to meet Spain's Prime Minister Pedro Sánchez to push his agenda for secession and freedom for the prisoners.

"We ask once again the acting Spanish PM to set the date and time to sit with us at a negotiating table," Torra said. "Today this is more necessary than ever before."

The prime minister's office responded that "the government of Spain has always been in favor of dialogue, but within the confines of the law."

Catalan pro-independence demonstrators sit in the street in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
Independence protesters gather in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
Riot police get ready in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
Riot police get ready in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
A man holds a Ikurrina or Basque flag close to Catalonia independence flag or ''Estelada'', during a protest by Basque pro-independence activists in support of Catalonia's independence movement following Spain's conviction of Catalan separatist leaders, in San Sebastian, northern Spain, Saturday, Oct. 19, 2019. Spain's Supreme Court on October 14 sentenced 12 prominent former Catalan politicians and activists of illegally promoting the Catalonia region's independence. (AP Photo/Alvaro Barrientos)
Catalan pro-independence demonstrators pack the street in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
Catalan pro-independence demonstrators with an
Some thousands pro-independence basques activist march in a rally along La Concha beach in support of Catalonia's independence movement following Spain's conviction of Catalan separatist leaders, in San Sebastian, northern Spain, Saturday, Oct. 19, 2019. Spain's Supreme Court on October 14 sentenced 12 prominent former Catalan politicians and activists of illegally promoting the Catalonia region's independence. (AP Photo/Alvaro Barrientos)
Catalan pro-independence demonstrators pack the street in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
A man holds a Ikurrina or Basque flag close to Catalonia independence flag or ''Estelada'', during a protest by Basque pro-independence activists in support of Catalonia's independence movement following Spain's conviction of Catalan separatist leaders, in San Sebastian, northern Spain, Saturday, Oct. 19, 2019. Spain's Supreme Court on October 14 sentenced 12 prominent former Catalan politicians and activists of illegally promoting the Catalonia region's independence. (AP Photo/Alvaro Barrientos)
Thousands pro-independence basques activist march in a rally in support of Catalonia's independence movement following Spain's conviction of Catalan separatist leaders and calling their freedom, in San Sebastian, northern Spain, Saturday, Oct. 19, 2019. Spain's Supreme Court on October 14 sentenced 12 prominent former Catalan politicians and activists of illegally promoting the Catalonia region's independence. (AP Photo/Alvaro Barrientos)
Thousands pro-independence basques activist march in a rally in support of Catalonia's independence movement following Spain's conviction of Catalan separatist leaders, in San Sebastian, northern Spain, Saturday, Oct. 19, 2019. Spain's Supreme Court on October 14 sentenced 12 prominent former Catalan politicians and activists of illegally promoting the Catalonia region's independence. (AP Photo/Alvaro Barrientos)
A worker inspects a vandalize shop in Barcelona, Spain, Saturday, Oct. 19, 2019. Masses of flag-waving demonstrators demanding Catalonia's independence and the release from prison of separatist leaders jammed downtown Barcelona on Friday as the northeastern Spanish region endured its fifth straight day of unrest. On Friday, the demonstrations were mostly peaceful, though police clashed with a few hundred young protesters who hurled bottles, eggs and paint at the gates of the police headquarters in the center of the city. Large trash containers were burned before police responded, using rubber bullets and tear gas to disperse the crowds. (AP Photo/Bernat Armangue)
A damaged traffic light, following Friday clashes between protestors and police, in Barcelona, Spain, Saturday, Oct. 19, 2019. Masses of flag-waving demonstrators demanding Catalonia's independence and the release from prison of separatist leaders jammed downtown Barcelona on Friday as the northeastern Spanish region endured its fifth straight day of unrest. On Friday, the demonstrations were mostly peaceful, though police clashed with a few hundred young protesters who hurled bottles, eggs and paint at the gates of the police headquarters in the center of the city. Large trash containers were burned before police responded, using rubber bullets and tear gas to disperse the crowds. (AP Photo/Bernat Armangue)
Demonstrators throw stones at police during clashes in Barcelona, Spain, Friday, Oct. 18, 2019.The Catalan regional capital is bracing for a fifth day of protests over the conviction of a dozen Catalan independence leaders. Five marches of tens of thousands from inland towns are converging in Barcelona's center for a mass protest. (AP Photo/Emilio Morenatti)
Protesters march into the city on the fifth day of protests over the conviction of a dozen Catalan independence leaders in Barcelona, Spain, Friday, Oct. 18, 2019. Various flights into and out of the region are cancelled Friday due to a general strike called by pro-independence unions and five marches of tens of thousands from inland towns are expected converge in Barcelona's center on Friday afternoon for a mass protest with students to and workers who are on strike. (AP Photo/Joan Mateu)
A woman crosses through a street full of rubble during clashes between police and Catalan pro-independence protestors in Barcelona, Spain, Friday, Oct. 18, 2019.The Catalan regional capital is bracing for a fifth day of protests over the conviction of a dozen Catalan independence leaders. Five marches of tens of thousands from inland towns are converging in Barcelona's center for a mass protest. (AP Photo/Bernat Armangue)
National police officers clash with demonstrator during clashes in Barcelona, Spain, Friday, Oct. 18, 2019.The Catalan regional capital is bracing for a fifth day of protests over the conviction of a dozen Catalan independence leaders. Five marches of tens of thousands from inland towns are converging in Barcelona's center for a mass protest. (AP Photo/Emilio Morenatti)
Protesters are dispersed by teargas thrown by national police officers, during clashes in Barcelona, Spain, Friday, Oct. 18, 2019.The Catalan regional capital is bracing for a fifth day of protests over the conviction of a dozen Catalan independence leaders. Five marches of tens of thousands from inland towns are converging in Barcelona's center for a mass protest. (AP Photo/Emilio Morenatti)
Catalan pro-independence demonstrators pack the street in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)
Catalan pro-independence demonstrators pack the street in Barcelona, Spain, Saturday, Oct. 19, 2019. Barcelona and the rest of the restive Spanish region of Catalonia are reeling from five straight days of violent protests for the sentencing of 12 separatist leaders to lengthy prison sentences.The riots have broken out at nightfall following huge peaceful protests each day since Monday's Supreme Court verdict. (AP Photo/Manu Fernandez)