(CNN) -- Demonstrators stormed a provincial administration building in eastern Ukraine on Sunday and raised the Russian flag atop it, demanding the release of riot police accused of killing protesters in Kiev, the Ukrainian capital, in February.
Police were negotiating with the demonstrators, who have called for supporters to rally around the Regional Security Administration building in Donetsk, about 200 kilometers (120 miles) from the Russian border. Video of the negotiations was being streamed live online by local news outlets.
The protest is the latest challenge to Ukraine's embattled new government, which took power after a revolt that toppled pro-Russian President Viktor Yanukovych in February. There was no immediate response to the seizure from top officials in Kiev, where the jailed police are accused of killing protesters during the uprising against Yanukovych.
The separatists inside the building used a loudspeaker to call for formation of a "people's city council" for Donetsk.
"The Russians are trying to destabilize the situation in the country," Ukraine Interior Minister Arsen Avakov said in a post on his Facebook page Sunday. "Putin and Yanukovich have ordered and paid for another round of separatist disturbances in the East of the country, Lugansk, Donetsk, Kharkov."
The pro-Russian "paid provocateurs" were trying to "bring blood and victims," but Ukrainian police have been ordered to "take the situation under control without spilling blood," Avakov said.
"The police will not shoot people due to a bunch of paid provocateurs," the interior minister said. "There are people who were deceived and who were paid among the protestors."
The protests led Ukraine's acting President Oleksandr Turchinov to cancel a trip to Lithuania Sunday, his spokesman said. Turchinov, who also serves as parliament speaker, was scheduled to travel there to meet with speakers from European Union states.
Turchinov will instead meet with law enforcement chiefs and take "personal control" of the response to the protests, the spokesman said.
Ukrainian Prime Minister Arseniy Yatsenyuk announced on live television Sunday evening that he would travel to his country's eastern regions "to dismiss their fears."
Yatsenyuk said he would offer to decentralize power and state financial support for local businesses.
In mid-March, Ukraine's new government warned that pro-Russian forces in other regions might attempt to follow the model used to wrest the Crimea region from Ukraine.
Yatsenyuk said demonstrations by what he called "political tourists" with foreign passports were already under way; Andrii Parubii, the secretary of the Ukrainian parliament's National Security and Defense Council, said protesters included "elite special units that are trying to arrive to Ukraine with weapons."
The Donetsk protest comes more than a month after pro-Russian forces seized government headquarters in Ukraine's semi-autonomous, Russian-majority Crimea region. A new administration was quickly put in place, backed by Russian troops and local militias. A hastily called referendum on independence, condemned as unconstitutional by Ukraine's government and the West, led to the territory's swift annexation by Moscow, a process completed by March 20.
CNN's Claudia Dominguez contributed to this report.