Viktor Yanukovych has said he will not resign as Ukrainian prime minister after losing the presidential election.
Opposition supporters prevented Yanukovych joining a cabinet meeting
He also submitted legal challenges to contest the preliminary results of the election, claiming multiple abuses.
Earlier, supporters of the apparent winner, Viktor Yushchenko, prevented Mr Yanukovych entering the government compound to chair a cabinet meeting.
Mr Yushchenko said he considered the current government "illegal" since it lost a vote of confidence by MPs.
But outgoing President Leonid Kuchma has yet to sack them.
Mr Yushchenko gained more than half of the vote in the third and decisive round of the poll held last Sunday, a majority of more than two million votes.
However, he will not be proclaimed the winner until his rival exhausts all legal possibilities to challenge his victory.
Mr Yanukovych sent his complaint to the Central Electoral Commission, which now has two days to examine it. After that he has a right to appeal to the Supreme Court.
"It is my firm position that I have no intention of resigning," he said. "They are insisting on this because, before as now, they are quaking in their shoes. We will soon say what we have to say."
In Ukraine, the president is the most powerful post in the country, while the prime minister is usually a non-partisan managerial figure in parliament. Prime ministers are expected to resign when a new president is elected.
However, the presidential authority will be considerably reduced after constitutional amendments adopted on the eve of the final round come into force on 1 September 2005.
Earlier on Wednesday, Mr Yushchenko kept up the pressure on his rival by calling on thousands of supporters gathered on Independence Square to prevent Mr Yanukovych from participating in a cabinet meeting.
The meeting was postponed after the opposition blockaded the government compound. Later the blockade was lifted and the cabinet held its meeting, but without the prime minister.
In an interview with the Russian Izvestia daily on Wednesday, Mr Yanukovych confirmed that he would never recognise Mr Yushchenko's victory.
He pledged to continue the fight by forming "tough opposition inside and outside the parliament" and forming parliamentary majority government, which will be in opposition to Mr Yushchenko if he becomes president.