Ukraine could need bailout loans amounting to £21 billion just to get through the next two years, acting government officials have warned.

Ukrainian MPs are expected to vote on the new cabinet line-up today as the interim government warned "unpopular steps" would be taken to stabilise the economy and political situation.

The vote comes as "criminals wearing military fatigues" seized the regional government and parliament headquarters on Ukraine's Crimea peninsula this morning.

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The Russian flag has been raised over the two buildings in the capital, Simferopol. Ukraine security forces are now on alert after the building was overtaken during the early hours of this morning.

PM-designate Arseniy Yatsenyuk and other new ministers were presented to Kiev's Independence Square yesterday evening. The 39-year-old served as economy minister, foreign minister and parliamentary speaker before ousted President Viktor Yanukovych took office in 2010.

Mr Yatsenyuk, who is expected to to lead the cabinet until early presidential elections, told the BBC "extremely unpopular steps" would be necessary to fix the "desperate financial plight" he said was created by a "corrupted" previous government.

"We are on the brink of a disaster and this is the government of political suiciders. So welcome to hell," he said.

Shape Created with Sketch. In pictures: Crisis in Ukraine Show all 11 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. In pictures: Crisis in Ukraine 1/11 Demonstrations in Crimea Crimean Tatars drag away a police officer in front of a local government building in Simferopol AP 2/11 Demonstrations in Crimea Pro-Russian activists pray outside the Crimean Parliament building in Simferopol EPA 3/11 Demonstrations in Crimea Crimean Tatars hold flags during rallies near the Crimean parliament building in Simferopol Reuters 4/11 Demonstrations in Kiev Young girls chant the song 'Glory to Ukraine' at Independence Square in central Kiev AFP/Getty 5/11 Demonstrations in Crimea A man receives medical treatment after he was injured in clashes during rallies near the Crimean parliament building Reuters 6/11 Demonstrations in Crimea Pro-Ukrainian activists hold placards reading "Crimea +Ukraine is love" during a rally in front of the Crimean parliament in Semfiropol AFP 7/11 Demonstrations in Kiev Protestors capture a military armoured vehicle in central Kiev AFP/Getty 8/11 Demonstrations in Kiev An old man stands with an Ukrainian flag on Kiev's Independence Square AFP/Getty 9/11 Demonstrations in Kiev A man lays flowers at one of the barricades heading to Kiev's Independence Square AP 10/11 Demonstrations in Kiev Flowers cover the ground and barricades where protesters were killed in a recent clash with riot police in Kiev's Independence Square AP 11/11 Demonstrations in Kiev A self-defense unit patrolling the city centre in Kiev, Ukraine AP 1/11 Demonstrations in Crimea Crimean Tatars drag away a police officer in front of a local government building in Simferopol AP 2/11 Demonstrations in Crimea Pro-Russian activists pray outside the Crimean Parliament building in Simferopol EPA 3/11 Demonstrations in Crimea Crimean Tatars hold flags during rallies near the Crimean parliament building in Simferopol Reuters 4/11 Demonstrations in Kiev Young girls chant the song 'Glory to Ukraine' at Independence Square in central Kiev AFP/Getty 5/11 Demonstrations in Crimea A man receives medical treatment after he was injured in clashes during rallies near the Crimean parliament building Reuters 6/11 Demonstrations in Crimea Pro-Ukrainian activists hold placards reading "Crimea +Ukraine is love" during a rally in front of the Crimean parliament in Semfiropol AFP 7/11 Demonstrations in Kiev Protestors capture a military armoured vehicle in central Kiev AFP/Getty 8/11 Demonstrations in Kiev An old man stands with an Ukrainian flag on Kiev's Independence Square AFP/Getty 9/11 Demonstrations in Kiev A man lays flowers at one of the barricades heading to Kiev's Independence Square AP 10/11 Demonstrations in Kiev Flowers cover the ground and barricades where protesters were killed in a recent clash with riot police in Kiev's Independence Square AP 11/11 Demonstrations in Kiev A self-defense unit patrolling the city centre in Kiev, Ukraine AP

On Wednesday, the US Secretary of State John Kerry said it was considering $1 billion (£600 million) in US loan guarantees and additional funding to help Kiev, as well as possible budget support, but said no firm decisions had been made.

"We are formulating initially a $1 billion loan guarantee with some other pieces, but we are also looking at the possibility of additional assistance," Mr Kerry said. The Obama administration was discussing the matter internally, he said.

One of the first jobs for Mr Yatsenyuk and other members of his new Cabinet will be seeking outside financial help from the European Union and the International Monetary Fund.

The IMF last agreed to loan Ukraine $15 billion in 2010, but froze the deal in 2011 after Kiev failed to implement the required reforms, including removing gas price subsidies.

Additional reporting by agencies