Ukraine's parliament has voted in favour of sacking the government over its recent gas deal with Russia.
Prime Minister Yekhanurov says he will stay in office for now
A no-confidence vote was backed by 250 of the assembly's 450 deputies.
But President Viktor Yushchenko has questioned its legitimacy. He plans to challenge it in the Constitutional Court, his spokeswoman says.
Ukraine agreed to double its payments to Russia for gas after Moscow switched off its supplies for three days on 1 January demanding a four-fold hike.
President Yushchenko has described the deal as a victory for the country as it still avoids the Russian demand, and the government has pledged consumer gas prices will stay stable.
But initial relief has given way to growing concern that the accord does not safeguard jobs and industry, reports the BBC's Helen Fawkes in Kiev.
The no-confidence motion was put forward during a lively session in the parliament.
It is not clear if parliament has the power to sack the government as Ukraine is currently in the middle of political reforms, says our correspondent.
The cabinet will continue to act as an interim administration until a parliamentary election in March, President Yushchenko said.
Some Ukrainian politicians believe the vote is part of a plan by Moscow to destabilise the country.
"People just wanted to play around; this will have no effect," Prime Minister Yuri Yekhanurov told reporters.
But our correspondent says the vote is a huge blow to the president, coming just days after Kiev resolved its gas crisis with Russia.
Defending the deal before parliament, the prime minister earlier said his government "was guided and will continue to be guided by the national interests of Ukraine".
He said he struck the deal - rather than referring the matter to international arbitrators - in order to avoid months of gas shortages.
There are fears Russia could raise gas prices again when the deal's six-month term has elapsed.
Ukraine had been paying only $50 (£28) per 1,000 cubic metres for its gas until the deal was reached.
It has now agreed to pay $95 (£54) per 1,000 cubic metres of gas, almost double the previous price.
Ukraine's former Prime Minister Yulia Tymoshenko has launched a legal challenge against the energy deal.
The no-confidence vote marks the second time in six months that a Ukrainian government has been sacked.