Dozens of pro-Russian protesters attacked a police station in the city of Horlivka on Monday, hurling rocks and smashing windows. There was thick white smoke rising from the building's entrance as the separatists raised the Russian flag on its roof.

At 9:00 a.m. (0600 UTC) Monday morning, a deadline issued by authorities passed, which had called on all pro-Russian gunmen who have seized government buildings across Ukraine's eastern region to put down their weapons. There was no immediate sign of action on the part of Ukrainian authorities to force them out.

Pro-Russian gunmen have now seized or blocked government buildings in at least nine cities, demanding more autonomy from the Ukrainian government and closer ties with Moscow. The government in Kyiv, along with Western officials, has accused Moscow of instigating the protests, saying the events are similar to the situation that unfolded in Crimea, which ended with its annexation by Russia.

After the separatists ignored Kyiv's ultimatum, acting President Oleksander Turchynov indicated that holding a nation-wide referendum on Ukraine's status might be possible, along with presidential elections. Turchynov said he was confident the vote, which would be held May 25, would show that Ukrainians do not want their country broken up into federations.

Russian Foreign Minister Sergei Lavrov said Monday that Ukraine's east should have a say in drafting the referendum.

"Let every political actor and every region without exception voice its interests and based on that we will look for a common denominator and then we will get a constitution that really unites and guarantees the interest of the people," Lavrov told reporters in Moscow.

Germany sees 'signs' of Russian support

The German government said Monday it was seeing indications that the pro-Russian militias in eastern Ukraine were receiving support from Moscow.

"The government is worried about the further aggravation of the situation in the east of Ukraine," said Christiane Wirtz, a spokeswoman for Chancellor Angela Merkel. "There are many signs that the armed groups active in eastern Ukraine are receiving support from Russia."

"A look at the appearance, uniforms and weaponry of some of these groups hardly suggests that they are defense forces spontaneously formed by civilians," she added.

Wirtz said these indications mean Russia has "a particular responsibility to prevent a further escalation, and to contribute to stabilizing the situation in Ukraine."

In response to Kyiv and Western accusations that Russia is preparing a military intervention in the Ukraine's east, Lavrov said he did "not even want to speculate. We do not meddle in the affairs of Ukraine."

It is "not in Russia's interest to destabilize the situation in Ukraine," he said.

dr/hc (AP, AFP, Reuters, dpa)