PODGORICA, Montenegro (AP) — Montenegro’s prime minister-designate on Sunday protested the outgoing government’s decision to expel the Serbian ambassador from the small Balkan country just days before the planned inauguration of a new, pro Serb Cabinet.

“Such acts are not in the spirit of the European path and good regional cooperation of friendly countries,” Zdravko Krivokapic tweeted. “The outgoing regime, even in its last days, does not shy away from the polarization of society and the deepening of divisions.”

Montenegro’s Foreign Ministry cited “long and continuous meddling in the internal affairs of Montenegro” as the reason for ordering the Serbian ambassador to leave the country. In a tit-for-tat move on Saturday, Serbia’s Foreign Ministry said it responded in a “reciprocal manner” and proclaimed the Montenegrin ambassador to Serbia persona non grata.

The diplomatic dispute added to already tense relations between the two neighboring Balkan states that were part of the same country before an independence referendum in 2006 led to Montenegro splitting away.

Montenegro remains deeply divided among those seeking closer ties with traditional Slavic allies Serbia and Russia and those who view Montenegro as an independent state allied with the West.

The long-ruling pro-Western Democratic Party of Socialists was defeated in an August election by a pro-Serb coalition whose government is set to be voted into office during a parliamentary session next week. The DPS-led government defied Serbia and Russia to join NATO in 2017.

The outgoing authorities have accused Serbia of meddling in the election and aiding pro-Serb political forces in Montenegro with the goal of installing allies in power and regaining influence.

“The new government will work to improve Montenegro’s relations with Serbia, we will promote a truly good neighborly policy with Belgrade, as well as with everyone in the region, on the principle of sovereignty, independence and non-interference in the internal affairs of other countries,” Krivokapic tweeted.