Pro-Russian activists in the eastern Ukrainian city of Donetsk have declared independence from Kiev, and pledged to hold a referendum to legitimise its separation.
An unidentified pro-Russian activist in the provincial government headquarters in Donetsk said: "Seeking to create a popular, legitimate, sovereign state, I proclaim the creation for the sovereign state of the People's Republic of Donetsk."
The activists, who have promised to hold a referendum on joining the Russian Federation before 11 May, also requested that the Russian President Vladimir Putin sends peacekeeping troops to the region, Interfax Ukraine reports.
Ukraine's acting President Olexander Turchynov was quoted by the Guardian as saying that the separatist call in Donetsk and pro-Russian protests in two other eastern cities were proof of a 'second stage' of Russian operations 'playing out the Crimean scenario'.
Interim Prime Minister Arseniy Yatsenyuk also held Moscow responsible for the turmoil, and called it a 'pretext for dispatching troops across the border'.
"The plan is to destabilise the situation, the plan is for foreign troops to cross the border and seize the country's territory, which we will not allow," Yatsenyuk said, noting that the Russian soldiers are stationed within 30km of the border.
Thousands of pro-Russian activists had stormed and seized administration buildings in Donetsk, Luhansk and Kharkiv on Sunday, demanding Crimea-style referendums on joining Russia.
White House spokesperson Jay Carney attributed these moves to increased Russian pressure on Ukraine, and warned Putin against further military intervention in the country.
However, Russian Foreign Minister Sergei Lavrov wrote in the Guardian that Russia is doing its best to promote stabilisation in Ukraine, and instead held the West guilty for the growing unrest and violence in the former Soviet Republic.
"They have been trying to compel Ukraine to make a painful choice between east and west, thus further aggravating internal differences," Lavrov said.