Summary Ukraine accused Moscow of "aggression" on Saturday on its eastern border.
SLAVYANSK (AFP) - Ukraine accused Moscow of "aggression" on Saturday after Kalashnikov-wielding gunmen seized two security buildings in its restive eastern rust belt amid spreading protests demanding the Russified region join Kremlin rule.
The coordinated attacks and a series of gunfights between militants and police in two eastern towns underscored the volatility of the crisis ahead of first direct talks between EU and US diplomats and their Moscow and Kiev counterparts in Geneva on Thursday.
They also threaten to lead to further violence as far right forces which hold sway over the ex-Soviet state's western regions, and which played a decisive role in this winter's anti-government protests, watch the nation of 46 million veer toward a possible breakup.
"The authorities of Ukraine view today's events as a display of aggression by the Russian Federation," Interior Minister Arsen Avakov wrote on his Facebook page.
Kiev said Ukraine's interim 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."
But Moscow said Lavrov firmly rejected the accusation and "noted that similar claims... have been made by Washington, although we still have not been presented with any concrete proof".
Acting Ukrainian president Oleksandr Turchynov convened an emergency security meeting after his interior minister reported that a "gunfight" had erupted between local security forces and militants who had attacked a police station in the eastern town of Kramatorsk.
The meeting broke up around midnight (2100 GMT) with no announcement except that the participants were considering measures to allow " normalisation of the situation in eastern Ukraine".
Ukraine's interim government has been facing relentless pressure from Russia since its February ouster of an unpopular Kremlin-backed president and decision to seek closer ties with the West.
The seizures highlight how little sway Kiev's untested leaders have over pro-Russians who have since April 6 also controlled the Donetsk government seat and a state security building in the nearby eastern city of Lugansk.
Moscow has massed tens of thousands of troops on Ukraine's eastern border after annexing the Black Sea peninsula of Crimea and nearly doubled the rates it charges Kiev for gas.
Russia is now ready to demand prepayment from the cash-strapped government for future gas deliveries or halt supplies -- a move that would impact at least 18 EU countries and deepen the worst East-West standoff since the Cold War.
A letter obtained by AFP and dated April 11 showed European Commission President Jose Manuel Barroso calling for a common EU response to President Vladimir Putin's latest energy warning.
A note sent by Putin on Thursday cautioning that gas transits through Ukraine may cease due to Kiev's debts to Moscow "raises serious issues for Europe's collective energy security", Barroso wrote.
Barroso said the issue would be raised at a meeting on Monday of EU foreign ministers and in a conference call with the 28-nation bloc's energy chief.
US Vice President Joe Biden will travel to Ukraine on April 22 to stress support for Kiev and steps to improve its energy security, a White House statement said Saturday.
