Pro-Russian separatists have retained control of key government buildings in eastern Ukraine, despite a vow by the country's prime minister to cede more power to the region amid rising tensions between Russia and the international community.

The armed occupiers, who demand greater autonomy, remained in control of the occupied buildings in the cities of Donetsk and Luhansk on Saturday, a day after Prime Minister Arseniy Yatsenyuk told leaders in Donetsk that he favored a peaceful solution to the standoff.

The crisis escalated on Saturday, after armed men in camouflage uniforms seized a police department in the eastern city of Slaviansk, which is about 150km from the border with Russia.

In response to the latest occupation, Interior Minister Arsen Avakov said in a post on Facebook: "The response will be very tough, because there is a difference between protesters and terrorists."

Al Jazeera's Kim Vinnell, reporting from Donetsk, said pro-Russian protesters had stormed into the prosecutor-general's office there early on Saturday, but exited the building when riot police arrived.

"What this incident suggests is that the situation is still very fluid, and that the pro-Russian activists are still very active in this region," our correspondent said.

Meanwhile in Luhansk, negotiations between protest leaders and a delegation from Kiev are taking place inside an occupied police building, reported Al Jazeera's Hoda Abdel-Hamid.

"The protesters want guarantees because they don't trust the [Ukrainian] government," said our reporter, adding that the protesters also demanded the guarantee for amnesty and a south-eastern army "that would be within the framework of the national army, but led by local command".

Ukraine's eastern industrial heartland was the support base for Kremlin-friendly President Viktor Yanukovich, who was ousted in February after months of protests over his decision to ditch an EU trade pact in favor of closer ties with Moscow. Last month, the Crimea region voted to secede and was annexed by Russia.

The protesters in Donetsk, who have held the regional administration building since Sunday, initially called for a referendum on secession but later reduced the demand to one on autonomy, with the possibility of holding another later on whether the region would remain part of Ukraine or seek to become an autonomous region within Russia.

Eastern Ukraine has a high proportion of Russian-speakers and many of them fear that the acting government, which took over when Yanukovich fled to Russia in February, will repress them.

Threat of sanctions

Yatsenyuk said on Friday that abolishing local administrations controlled by Kiev is one of the steps to decentralize Ukraine.

He added that the grievances of eastern Ukraine would be addressed by the upcoming constitutional reform which will "satisfy people who want to see more powers given to regions".

However, he left the door open for storming the occupied buildings as a two-day deadline announced earlier this week passed without the separatists showing any sign of vacating.

Kiev and Western officials claim that Russia is whipping up tensions in the east, with the aim of establishing a pretext for sending in troops, an accusation denied by Moscow.

The G7 nations - the United States, Canada, France, Germany, Italy, Japan and the United Kingdom - have said that the group will support increasing sanctions against Russia if Moscow escalates the crisis in Ukraine.

But Russian President Vladimir Putin, whose troops have already massed along Ukraine's eastern border following their seizure of Crimea, only upped the stakes by threatening to cut off Ukraine's gas over unpaid bills.

The decision could limit the supplies of at least 18 European nations for the third time since 2006. Each of the previous interruptions also coincided with attempts by Ukraine to pull itself out of the Kremlin's sphere of influence.

PHOTO CAPTION

Pro-Russia activists occupying a government building in Luhansk held a press conference on April 11

Al-Jazeera