DONETSK: Ukraine faced a fresh secessionist crisis Monday when pro-Russians occupying the Donetsk government seat proclaimed independence from Kiev and vowed to hold a referendum on joining Kremlin rule.

The declaration and subsequent appeal for Russian military help should Kiev's new pro-Western leaders resist their independence drive put the nation of 46 million in danger of disintegration and added still more pressure on Western powers to act.

The ex-Soviet nation on the EU's eastern frontier continues to be watched by tens of thousands of Russian troops who had already annexed the Black Sea peninsula of Crimea in response to last month's ouster in Kiev of a Moscow-backed regime.

Several heavily Russified eastern regions now want to stage referendums on joining Russia when Ukraine holds snap presidential polls on May 25 that feature two frontrunners who both want to tie the vast country's future to Europe and break its historic dependence on its eastern neighbour.

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” in the region of about five million people.

Footage posted on YouTube showed one bearded Russian speaker telling the packed assembly from a podium: “Seeking to create a popular, legitimate, sovereign state, I proclaim the creation of the sovereign state of the People's Republic of Donetsk.”

The industrial eastern region's Ostrov (Island) news website reported that the activists later resolved to join the Russian Federation in a move similar to the one taken by Ukraine's Crimea peninsula last month.

The news site said the resolution was met with a huge roar and chants of: “(Russian President Vladimir) Putin, help!”

The Interfax news agency reported that the self-proclaimed leaders had also vowed to hold a regional sovereignty referendum no later than May 11.

More footage aired on 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.

Ukraine's latest bout of political turmoil prompted Prime Minister Arseniy Yatsenyuk to send his deputy Vitaliy Yarema to the region in order to establish a semblance of control.

The Donetsk administration building on Monday was surrounded by about 2,000 Russian supporters, some of them armed.

Pro-Russian protesters also remained in control of the headquarters of the security service of the eastern region of Lugansk. Activists freed the administration building in Kharkiv on Monday after occupying it overnight.

“People were tired and many went home to get some rest. Now we are waiting for the Kharkiv people to gather again and then we will see what we will do,”said a 28-year-old pro-Russian activist named Andriy.

Seeking to 'dismember Ukraine'

Ukraine's 39-year-old prime minister bluntly accused Russia of helping orchestrate the occupations in order to find an excuse for a full-out invasion that would punish Ukraine for its decision to seek a political and economic alliance with the West.

“There is a plan to destabilise the situation, a plan for foreign forces to cross the border and seize the territory of the country, which we will not allow,” Yatsenyuk told a government meeting in Kiev.

“This scenario is written by the Russian Federation and its only purpose is to dismember Ukraine.”

Moscow is now lobbying for Ukraine to be transformed into a federation that allows eastern regions to adopt Russian as a second state language and overrule some decisions coming from Kiev.

The Kremlin has argued the changes were needed because ethnic Russians had allegedly been coming under increasing attack from ultranationalist forces that helped the new leaders ride a wave of anti-government protests to power.

But Washington and its EU allies fear that Russia, having already annexed Crimea last month, is using the federation idea as an excuse to further splinter Ukraine by granting the Kremlin veto powers over Kiev's regional policies.

The new Kiev government approved a draft reform plan last week that would grant more powers to the regions in line with Western wishes but stopped well short of creating the federation sought by Russia.

And Yatsenyuk on Monday called federalisation a dangerous idea aimed at ruining Ukraine.

“Any call toward federalisation is an attempt to destroy the Ukrainian state,” said Yatsenyuk.

He added that the Kremlin's ambition was to turn “a part of Ukraine into a slave territory that was under the diktat of the Russian Federation.”