HORLIVKA, Ukraine (AP) -- A pro-Russian mob on Monday seized a police building and gun men took control of a military airport in Russian-leaning eastern Ukraine, defying government warnings that it was preparing to act against the separatists.
Dozens of angry men hurled rocks, smashed the windows and broke into a police station in the city of Horlivka not far from the border with Russia, and flew the Russian flag from the building. Hundreds of onlookers outside chanted "Referendum!" and "Russia!" A video posted online showed a policeman confronting a separatist, then being beaten by the mob and taken away in an ambulance. Other policemen switched their allegiance to the demonstrators.
The events in Horlivka were the latest sign of trouble in Russian-speaking eastern and southern regions, in which pro-Russian gunmen have seized or blocked government buildings in at least nine cities demanding more autonomy from the central government and closer ties with Russia. Later in the day, armed men in masks also seized control of a military airport outside the city Slovyansk, also in the Donetsk region.
The developments came as European Union foreign ministers met in Luxembourg to consider further sanctions against Russia, and three days ahead of a scheduled conference in Geneva involving diplomats from the United States, Russia, the European Union, Ukraine and Switzerland, which is intended to seek ways of defusing tensions.
Russia has warned the Kiev government against using force against the protesters in the east and has threatened to cancel the conference.
One of the men directing the raid in Horlivka introduced himself as a lieutenant colonel of the Russian army to a line of policemen who switched sides, but he did not state his full name. The man, dressed in green camouflage uniform, instructed them to obey their new chief and to attach St. George's ribbons to their uniforms, which have become a symbol of pro-Russian protesters in eastern Ukraine.
The episode fed into accusations from the government in Kiev and Western officials that the protests are being instigated by the Kremlin and that some of the insurgents are Russian agents.
Oleksandr Sapunov, one of the men who took part in storming the police building in Horlivka, said the insurgents were fighting against appointees of the Kiev government, including the local police chief, and wanted to appoint a leadership of their own.
"The people came to tell him that he is a puppet of the Kiev junta and they won't accept him," Sapunov said.
Acting Deputy Interior Minister Mykola Velichkovych acknowledged Monday that some police officers in eastern regions were switching sides. "In the east we have seen numerous facts of sabotage from the side of police," Velichkovych told reporters.
The events echoed those in Crimea, which was annexed by Russia last month after key regional facilities were seized by Russian troops aided by local militiamen.
Ever since pro-Russian President Viktor Yanukovych fled to Russia in late February, Russia has demanded constitutional reforms that would turn Ukraine into a loose federal state.
After refusing demands for a referendum by separatists in the east, acting President Oleksandr Turchynov indicated Monday that holding a nation-wide referendum on the nation's status was a possibility and that such a vote could be conducted on May 25, along with presidential elections. Turchynov expressed confidence that Ukrainians would vote against turning the country into a federation and against its break-up.
Meanwhile, a deadline set by the Ukrainian government for pro-Russian gunmen to leave government buildings in eastern Ukraine and surrender weapons passed early Monday, with no immediate sign of any action to force the insurgents out.
Turchynov had issued a decree Sunday that those protesters who disarm and vacate government offices in several cities in the Russian-leaning east of the country by 0600 GMT Monday will not be prosecuted. Turchynov vowed that a "large-scale anti-terrorist operation" would take place to re-establish control over those areas.
There was no immediate comment from the government on the deadline passing.
But Serhiy Taruta, governor of the Donetsk region, where government buildings in several cities, including the regional capital Donetsk, have been seized by pro-Russian gunmen, said an "anti-terrorist operation" was underway in the region, according to the Interfax news agency.
Taruta gave no details of what the operation would entail and there were no signs of increased police presence on the streets of Donetsk Monday. The governor usually does not have authority to launch such measures on his own and he was likely acting on the orders of top security officials in Kiev.
Taruta said the action would be aimed at "protecting the peace and order on our land, which today is being taken away from us by armed, aggressive fanatics cynically and cold-bloodedly," he was quoted as saying. "They are terrorists and we will not let them rule on our land." He did not provide any details of the operation.
The West has accused Moscow of fomenting the unrest.
"The fact is that many of the armed units that we've seen were outfitted in bulletproof vests, camouflage uniforms with insignia removed," U.S. Ambassador Samantha Power said during a UN Security Council session Sunday. "These armed units ... raised Russian and separatist flags over seized buildings and have called referendums and union with Russia. We know who is behind this."
Vadim Karasyov, a political analyst in Kiev, said the Kremlin was using the ousted president, Viktor Yanukovych, to help foment separatist tensions. "The Kremlin is implementing its scenario in the East, using Yanukovych and his loyalists, while Russian instructors are running the show," Karasyov said.
Russia has tens of thousands of troops massed along Ukraine's eastern border, and Western government have expressed fears that Moscow might use the violence in the mainly Russian-speaking region as a pretext for an invasion, in a repeat of events in Crimea weeks ago.
Russian Ambassador Vitaly Churkin denied Western and Ukrainian claims that Moscow was behind the violence, and told U.N. diplomats that Ukraine's interim government has been using radical neo-Nazi forces to destabilize its eastern region.
"Some people, including in this chamber, do not want to see the real reasons for what is happening in Ukraine and are constantly seeing the hand of Moscow in what is going on," Churkin said. "Enough. That is enough."
Maria Danilova and Nataliya Vasilyeva in Kiev and John-Thor Dahlburg in Brussels contributed to this report.