Ukraine's parliament has dismissed the foreign and interior ministers - key allies of President Viktor Yushchenko.
The president (right) plans to contest Mr Tarasiuk's sacking
Foreign Minister Borys Tarasiuk has been one of the country's most pro-Western officials.
Interior Minister Yuriy Lutsenko was also a key figure during the liberal "Orange Revolution" in 2004 that swept Mr Yushchenko to power.
The sackings come amid growing tensions between Mr Yushchenko and pro-Russian Prime Minister Viktor Yanukovych.
The president has said he will challenge the sacking of Mr Tarasiuk in Ukraine's Constitutional Court.
Under Ukraine's constitution, Mr Yushchenko is entitled to appoint the foreign minister.
The constitutional changes that came into effect earlier this year strengthened the prime minister's power and weakened those of the president.
The arrangement - which many experts in Ukraine say contains a number of contradictions - was billed as an effort to stabilise the country after the bitterly fought presidential polls in 2004.
But instead it has triggered a political tug-of-war for influence between Mr Yushchenko and Mr Yanukovych.