MOSCOW (AP) — A Moscow court has sentenced a participant in this summer's series of protests to four years in prison.

Konstantin Kotov was sentenced Thursday after being convicted of repeatedly calling for, or taking part in, unauthorized protests.

The conviction came a day after two other people were sentenced to 3 to 3 ½ years for using force against police during a July 27 protest in Moscow.

The protests are against Russian election officials disqualifying a dozen opposition and independent Moscow city council candidates. Government critics have said protesters are being put on trial to intimidate opposition supporters.

Investigators on Tuesday dropped rioting charges against five people but three others are still under investigation.

The protests, the largest in years, appear to reflect growing frustration with Russia's tightly controlled politics, which are dominated by President Vladimir Putin's allies in the United Russia party. Smaller protests have taken place recently in St. Petersburg, which will have mayoral and city council elections on Sept. 8.

About 300 people attended an authorized demonstration on Thursday in St. Petersburg, claiming that some independent candidates were denied registration.