Armed men in unmarked uniforms have taken up positions in the center of Luhansk in what appears to be part of a power struggle among the Russia-backed separatists who control the city in eastern Ukraine.

The region's separatist leader, Igor Plotnitsky, said the display of force by the masked, rifle-toting men in camouflage was a revolt by supporters of a fired police chief.

The independent Russian newspaper Novaya Gazeta said they were blocking administrative buildings in the provincial capital:

The masked armed men began to deploy in Luhansk after Plotnitsky fired the region's police chief, Igor Kornet, on November 20.

Hours later, Plotnitsky suggested that Kornet's allies were whipping up tension and had put uniformed men into the streets.

"I can say with confidence that the attempts by certain people to stay in power by destabilizing the situation...are futile, and in the very near future will be neutralized," Plotnitsky said in a statement.

The development did not appear to be in direct connection to the conflict between the separatists and Ukraine's government, but President Petro Poroshenko called a meeting of his National Security and Defense Council late on November 21.

"The Ukrainian armed forces are ready for all developments to ensure the safety of civilians," Poroshenko said in a statement.

The Organization for Security and Cooperation in Europe, which monitors the implementation of a much-violated cease-fire agreement with Ukraine, said on November 21 it had observed military-style vehicles and armed men in central Luhansk.

Parts of the Luhansk and Donetsk regions are held by Russia-backed separatists whose war against Kyiv's forces has killed more than 10,000 people since April 2014, when it erupted after Moscow fomented unrest following the ouster of Russia-friendly Ukrainian President Viktor Yanukovych.

In a statement posted on the Internet before Plotnitsky's statement, Kornet dismissed what he called "rumors about my dismissal" and said that the situation in what the separatists call the Luhansk People's Republic was "under the full control of forces of the law enforcement structures."

In the statement, Kornet claimed that police had "thwarted the activity of a Ukrainian sabotage-and-espionage group" that he said tried to enter the separatist-held territory overnight to carry out "sabotage and terrorist acts." He said that several people were detained and that police forces were "looking for other members of the group and their accomplices."

Kornet said that a probe had been opened against the director of the Luhansk television and radio company, Anastasia Shurkayeva, on suspicion of cooperation with Ukrainian intelligence. He also said that investigations had been opened into the chief of Plotnitsky's administration, Irina Teitsman, and the chief of the police unit responsible for security for members of the separatists' de facto government, Yevgeny Seliverstov, on suspicion of involvement in an alleged attempt to seize power in September 2016.

Kornet said that Plotnitsky gave the order to launch the investigations, but there was no immediate word from Plotnitsky himself.

With reporting by Novaya Gazeta, Reuters, and Meduza