Ukrainian Prime Minister Viktor Yanukovich called on his supporters to avert an "unconstitutional coup" led by Viktor Yushchenko, challenger to his presidency, Ukraine's state news agency reported.

"Dear friends, together we must do everything so that an unconstitutional coup in Ukraine does not happen," Yanukovich tolda rally by thousands of his supporters in front of Kiev's train station.

Most of the supporters were young men who arrived by train fromthe Donbass coalfield in the Russian-speaking east, the power baseof Yanukovich.

Yanukovich said what happened in the central and western parts of the country was illegal and the lawful government in the west has been overthrown. As from Friday, the opposition begun to blockthe Presidential Palace, the government and parliament buildings, he added.

On the other hand, he said, rallies in the south and the east were urging people to come to Kiev to restore order and security. However, he hoped that would never take place, as it would lead tobloodshed.

"I don't need power at the cost of spilled blood," Yanukovich said.

The country has been plagued by a spiraling political crisis over disputed presidential election results.

On Wednesday, the Central Election Commission declared Yanukovich the winner, saying he won 49.46 percent of the vote and Yushchenko 46.61 percent.

But Yushchenko rejected the results and claimed that the poll was rigged.

Since Sunday, hundreds of thousands of opposition supporters have gathered in Kiev and western cities, where West-leaning Yushchenko is popular, pressing for the installation of Yushchenkoas president.

Throngs of protesters set up a sprawling tent camp in the Independence Square in Kiev, braving freezing temperatures for five straight days.

Many municipal and state governments in the central and western regions have declared loyalty to Yushchenko, saying he is the lawfully elected president.

Ukraine's presidential elections are fast being internationalized as the results may become a watershed in the former Soviet republic's politics -- from traditional East-looking Yanukovich to West-leaning Yushchenko.

The United States and Europe have refused to accept the resultsand called for investigation into alleged irregularities while Russia has congratulated Yanukovich on his victory. Russian President Vladimir Putin has asked the West to have their hands off.

Outgoing Ukrainian President Leonid Kuchma, who supports Yanukovich, has called for political dialogue. In sharp contrast to Yushchenko, Yanukovich had been amazingly silent.