Opposition leader Mr Viktor Yushchenko declared victory in Ukraine's presidential election and took a symbolic oath of office today, warning that the country was on the verge of civil conflict.
Up to 200,000 protesters rallied outside an emergency session of Ukraine's parliament today demanding authorities admit they cheated in a presidential poll which showed the country's Moscow-backed prime minister had won.
Tonight demonstrators focused their protest on the president's administration office in Kiev and faced anti-riot police about 100 metres (yards) short of the building.
Mr Yushchenko has accused authorities of rigging Sunday's vote in favour of Prime Minister Mr Viktor Yanukovych and has announced a campaign of civil disobedience.
"Ukraine is on the threshold of a civil conflict," Mr Yushchenko told MPs gathered for an emergency session of parliament to consider an opposition request to annul the election results.
"We have two choices: either the answer will be given by the parliament, or the streets will give an answer."
"We are sliding towards the abyss. It is amoral and criminal to pretend nothing is happening in the country," parliamentary speaker Mr Volodymyr Lytvyn told deputies at the debate's start.
"We must act in good time otherwise the people will decide on our behalf tomorrow."
The parliamentary session ended without making any decision, since only 191 MPs - less than the 226 required to have a quorum - attended.
After the session ended, Mr Yushchenko swore an oath on a 300-year-old Bible. The Ukrainian constitution, however, stipulates that the president swears allegiance on a copy of the constitution. MPs chanted "Bravo, Mr President!"
Earlier, Mr Yushchenko and his allies had released a statement appealing "to the parliaments and nations of the world to bolster the will of the Ukrainian people, to support their aspiration to return to democracy."
The opposition will conduct "a campaign of civil disobedience" and "a non-violent struggle for recognition of the true results of the election."
The Election Commission's announcement that the Kremlin-backed Mr Yanukovych was ahead of Mr Yushchenko has galvanised anger among many of the former Soviet republic's 48 million people.
Official results, with more 99.48 per cent of precincts counted, showed Mr Yanukovych leading with 49.39 per cent to his challenger's 46.71 per cent. But several exit polls had found Mr Yushchenko the winner.
Russian President Mr Vladimir Putin said supporters of both candidates in the disputed Ukrainian election should act within the law, Russian news agencies reported today.
"Everything must remain legal. Ukraine is a big democratic state with a developed democratic system. There is no need to teach it democracy," he said in Lisbon, Itar-Tass news agency reported.
US and Western observers say the second round run-off presidential vote fell far short of international standards.
Washington warned of punitive measures if the Kiev leadership failed to investigate allegations of vote rigging and the European Union described the vote as "fraudulent".
In Brussels, the European parliament's chief observer said Sunday's run-off defied common sense and had more in common with a North Korean election.
In the nationalist heartland of western Ukraine, some 100,000 protesters marched through the city of Lviv to back Mr Yushchenko. Several thousand protesters massed in other western towns, including Lutsk and Khmelnitsky.
Mr Kuchma urged candidates in a disputed presidential election to hold consultations and told Western countries that statements critical of the poll could increase tension in the country.