Armed pro-Russian activists occupy the police station in the eastern Ukraine town of Slovyansk on Saturday, April 12, 2014.

Image Credit: AP Photo/Efrem Lukatsky

DONETSK, Ukraine -- Men in the uniforms of Ukraine's now-defunct riot police on Saturday occupied police headquarters in Donetsk, the eastern city that is one of the flashpoints of a wave of pro-Russia protests, hours after armed men seized local police headquarters and local branch of the Security Service in a nearby city.

The unrest in Donetsk and Slovyansk, about 90 kilometres to the north, were the latest shows of spiraling anger in eastern Ukraine, which has a large Russian-speaking population and was also the support base for Viktor Yanukovych, the Ukrainian president who was ousted in February after months of protests in the capital, Kyiv. Ethnic Russians in Ukraine's east widely fear that the authorities who took over after Yanukovych's fall will suppress them.

In Slovyansk, the mayor said the men who seized the police station were demanding a referendum on autonomy and possible annexation by Russia. Protesters in other eastern cities have made similar demands after a referendum in Crimea last month in which voters opted to split off from Ukraine, leading to annexation by Russia.

A regional news website said another police station had been seized in the town of Krasnyi Lyman, a town near Slovyansk, but that report could not immediately be confirmed. In Kramatorsk, another town near Slovyansk, protesters flew the flag of the Independent Donetsk Republic above the local administration building, according to Kramatorsk's news website.

Witnesses said the men who entered the police building in Donetsk were wearing the uniforms of the Berkut, the feared riot police squad that was disbanded in February after Yanukovych's ouster. Berkut officers' violent dispersal of a demonstration in Kyiv in November set off vast protests in the capital that culminated in bloodshed in February when more than 100 people died in sniper fire; the acting government says the snipers were police.

It was not immediately clear if the men who occupied the Donetsk police building had made any demands, but the Donetsk police chief said on national television that he was forced to offer his resignation. Interfax Ukraine reported that pro-Russian protesters had invited the former police chief to resume his duties.

In Slovyansk, about 20 men in balaclavas armed with automatic rifles and pistols were guarding the entrance to the police station in the city of about 120,000 people, and another 20 were believed to be inside. They wore St. George's ribbons, which have become a symbol of pro-Russian protesters in eastern Ukraine. The ribbons were originally associated with the Soviet Union's victory in World War II.

A masked guard in Slovyansk, who gave his name only as Sergei, told The Associated Press they have "only one demand: a referendum and joining Russia."

The man said they seized the building because they wanted to protect it from radical nationalists from western Ukraine and "the junta who seized power in Kyiv."

"We don't want to be slaves of America and the West," he said. "We want to live with Russia."

The Interior Ministry said in a statement that the attackers used tear gas and stun grenades when they stormed the building, injuring three policemen. The attackers' goal was to seize arms from the police station, authorities said, adding that there were about 40 automatic rifles and 400 pistols as well as ammunition inside.

The Interior Ministry reporter later on Saturday that men from the same group have seized the building of the local Security Service.

A video from the scene showed one man carrying a sniper rifle. An AP reporter saw another man loading the magazine of a pistol at the police station.

Interior Minister Arsen Avakov pledged a "very tough response" to the seizure while local media reported special forces dispatched to the area.

Local sympathizers brought tires to the police station to start building barricades. Gunshots rang out in the background in a video from the scene after an armed man shouted to a cameraman to stop recording.

An Associated Press crew saw about 10 men wearing camouflage and carrying automatic rifles at the entrance to the town late Saturday afternoon.

Businessman Petro Poroshenko, the front-runner in the presidential race, on Saturday lambasted Ukraine's fledging government of inaction in the face of unrest in eastern Ukraine.

The Kyiv authorities and the United States have accused Russia of fomenting the unrest in the east and seeking to use it as a pretext for sending in troops. Russia has reportedly massed forces in areas near the Ukrainian border.

But Mayor Nelya Shtepa told the AP that she held talks with the protesters and said they were local residents, not Russians.

"They told me: 'We don't have anything against you,' " she said, adding that the men said they "want to be heard, want a dialogue with authorities in Kyiv."

Protesters, who have held the administration building in Donetsk since Sunday, initially called for a referendum on secession but later reduced the demand to a vote on autonomy within Ukraine with the possibility of holding another later on whether to join Russia.

Russia's Foreign Ministry on Friday warned the Ukrainian government against using force against protesters, saying that such action would derail the talks on settling the crisis between the United States, the European Union, Russia and Ukraine set for next week, as well as any other diplomatic efforts.

Russian Foreign Minister Sergey Lavrov pressed the complaint in a telephone call with his Ukrainian counterpart, Andriy Deschytsia, on Saturday.

Lavrov told Deschytsia of "the unacceptability of the constant threats from Kyiv to storm buildings held by protesters," according to a Foreign Ministry statement.

News from © The Associated Press, 2014