DONETSK, Ukraine - Ukraine was threatened with disintegration Monday as pro-Kremlin militants seized government buildings in the eastern city of Donetsk, declared independence and vowed to vote on joining Russia.
The activists proclaimed the creation of a "people's republic" and appealed to Russian President Vladimir Putin to send a "peacekeeping contingent of the Russian army" to support them.
Ukraine accused Russia of fomenting the unrest and in Washington, the White House responded by calling on Moscow to stop efforts to "destabilise Ukraine" and threatened sanctions.
But Moscow brushed off the accusations and called the latest trouble a sign of Kiev's Western-backed leaders' ineptitude and illegitimacy.
The Cold War-style war of words came as Russian troops remained massed on the Ukrainian border.
Since Russia annexed Crimea, several mainly Russian-speaking eastern regions have seen calls for referendums on joining Russia when Ukraine holds snap presidential polls on May 25.
The political pressure on Kiev's embattled leaders reached boiling point on Sunday when thousands of activists chanting "Russia!" seized administration buildings in Kharkiv and Donetsk as well as the security service headquarters in the eastern region of Lugansk.
The Donetsk activists went one step further on Monday by proclaiming the creation of a sovereign "people's republic".
A video posted on YouTube showed one bearded Russian speaker telling the packed assembly: "Seeking to create a popular, legitimate, sovereign state, I proclaim the creation of the sovereign state of the People's Republic of Donetsk."
Ukraine's Channel 5 television showed an unidentified speaker asking Putin to send a "peacekeeping contingent of the Russian army" to Donetsk to help the region stand up to Kiev's rule.
'Stop pointing the finger'
Ukraine's acting president, Oleksandr Turchynov, accused Russian "special services" of being behind the uprising and ordered extra security personnel to the restless region.
"These actions are meant to destabilise the country, overthrow the Ukrainian government, torpedo the elections and tear our country to pieces," Turchynov said in a nationally televised address.
The Russian foreign ministry responded with a toughly worded statement telling Kiev to "stop pointing the finger at Russia, blaming it for all the problems in today's Ukraine."
But the White House put the onus back on Moscow by describing the latest developments "as the result of increasing Russian pressure on Ukraine."
"We call on President Putin and his government to cease efforts to destabilise Ukraine," White House spokesman Jay Carney said.
Washington's concern underscores the trouble Kiev may have in bringing order to Ukraine's eastern industrial heartland - a region with ancient cultural and trade ties to Russia.
The Donetsk administration building on Monday remained surrounded by about 2,000 Russia supporters - some of them armed.
Militants also seized the Donetsk security service headquarters while rival rallies gripped the heart of the nearby city of Kharkiv after its own administration building was occupied briefly overnight.