Kalashnikov-wielding gunmen on Saturday seized a police station and a security building in Ukraine's restive eastern industrial heartland amid spreading protests to press for the heavily Russified region to join Kremlin rule.
The coordinated attacks and a subsequent raid by a few hundred pro-Russian protesters on the police headquarters of the local capital Donetsk underscored the volatility of the crisis ahead of peace talks between EU and US diplomats and their Moscow and Kyiv counterparts in Geneva on Thursday.
Ukraine's interim leaders have been facing unceasing pressure from Russia since their February ouster of an unpopular Kremlin-backed president and decision to seek closer ties with the West.
Moscow has massed tens of thousands of troops on Ukraine's eastern border after annexing its Black Sea peninsula of Crimea and nearly doubled the rates it charges Kyiv for gas.
Russia is now ready to demand prepayment from the cash-strapped government for future gas deliveries or halt supplies — a cutoff that would impact at least 18 EU countries and add further urgency to the worst East-West standoff since the Cold War.
But the seizures more immediately highlight how little sway Kyiv's untested leaders have over pro-Russians who have since April 6 controlled the Donetsk government seat and a state security building in the nearby eastern city of Lugansk.
Ukrainian Prime Minister Arseniy Yatsenyuk visited the region on Friday in a failed bid to pacify protesters with a vague promise of more sweeping local rights.
The morning police station raid and a subsequent attack of the regional security service centre happened in Slavyansk — a riverside town of 100,000 about 35 miles north of the regional capital Donetsk.
Ukraine's interior ministry said the first assault was led by 20 "armed men in camouflage fatigues" whose main purpose was to seize 20 machine guns and 400 Makarov guns stored in the police headquarters "and to distribute them to protesters."
"Our response will be very severe," Interior Minister Arsen Avakov wrote on his Facebook page.
"There is zero tolerance for armed terrorists."
An AFP reporter saw the Slavyansk police station being surrounded by armed men in masks and camouflage who had set up a barricade of old tires and dumpsters in front of the police headquarters.
The gunmen aggressively shoved aside Western reporters and only allowed Russian-speaking media anywhere near the building.
"The entire city ... will defend the guys who seized this building," Slavyansk Mayor Neli Shlepa told Russia's Life News television outside the police headquarters.
The interior ministry said some of the same gunmen had later occupied the city's state security service building.
"The protest participants are continuing to arm themselves with weapons seized from the police," the interior ministry said in a statement.
Kyiv blames Russian agents
Ukraine's interior minister said that a separate group of assailants had also unsuccessfully tried to seize the Donetsk prosecutor's office.
But an AFP reporter in the city saw about 200 pro-Russian protesters armed with clubs and sticks storm the police headquarters and meet no resistance from anyone inside.
A few dozen anti-riot police who arrived at the scene were instead seen sporting orange and black ribbons symbolising support for Russian rule — a vivid sign of Kyiv's slipping hold on Ukraine's eastern rust belt.
The Donetsk administration center is already being held by gunmen who have proclaimed the creation of their own "people's republic" and called on President Vladimir Putin to send Russian troops into eastern Ukraine.
The interior minister had on Wednesday issued a veiled 48-hour ultimatum for the Donetsk separatists to lay down their arms or face the possible of use of force.
But no action followed and Russia warned on Friday that any use of force wound result in Moscow boycotting the Geneva talks.
Ukraine's embattled premier promised during an unannounced visit to Donetsk on Friday to grant more powers to the country's regions and protect the east's right to use the Russian language.
Kyiv has previously said it was ready to back partial devolution while stopping well short of creating the federation sought by Russia.
But the Donetsk and Lugansk gunmen also want to stage independence referendums coinciding with snap presidential polls Ukraine will stage on May 25.
Ukraine's new authorities reject that condition because a similar vote last month in Crimea led to the Black Sea peninsula's annexation by Russia.
Both Western leaders and Kyiv have accused the Kremlin of orchestrating the unrest in order to justify a possible future invasion of eastern Ukraine — a charge Moscow flatly denies.
Kyiv said that Ukrainian Foreign Minister Andriy Deshchytsya told his Russian counterpart Sergei Lavrov by telephone on Saturday to "stop the provocative activities of Russian special services in the eastern regions of Ukraine."