Protesters have taken over government buildings in Kiev amid reports that President Viktor Yanukovych has left Ukraine's capital.
peaking on Saturday morning, opposition leader Vitaly Klitschko claimed the President had fled and renewed calls for his resignation.
"Today he left the capital," he told an emergency session of parliament. "Millions of Ukrainians see only one choice - early presidential and parliamentary elections."
BBC correspondents said the President's offices appeared to be unguarded and protesters had gained control of much of the government district, including the presidential administration building.
"He's not here, none of his officials or anyone linked directly to the administration are here," Ostap Kryvdyk, a protest leader, told reporters in the grounds.
Reuters quoted a "senior security source" who claimed Mr Yanukovych was still in the country.
“Everything is ok with him,” the source said. “He is in Ukraine.” Asked whether the embattled leader was in the capital, he replied: “I cannot say.”
Hanna Herman, a close aide of the President, told reporters he was visiting the city of Kharkiv in east Ukraine, where many of his supporters are based.
Thousands of protesters remain on the streets of Ukraine despite a deal signed on Friday aiming to end the political crisis.
Parliament approved the pact mediated by European foreign ministers after days of violent clashes between demonstrators and police in Kiev that left an estimated 77 people dead.
The deal, signed by the government and opposition, could free former Prime Minister Yulia Tymoshenko, who has spent more than two years in jail for what supporters say are politically motivated charges.
The 2004 constitution was to be restored within 48 hours and a national unity government formed within 10 days before constitutional reform starts to balance the President's powers with that of government and parliament.
A presidential election will be held no later than December 2014 and an investigation into acts of violence will be monitored by the Council of Europe.
The agreement promises that authorities will not impose another state of emergency and "refrain from the use of violence" after reports that police opened fire on protesters.
But it may be too little, too late to pacify anti-government protesters who united despite dramatically differing political views with the sole aim of ousting Mr Yanukovych.
Opposition leaders were reportedly booed on Friday as they spoke to crowds following the deal, which many do not trust.
William Hague. the Foreign Secretary, called the agreement an "important first step" towards resolution.
He added: “I urge all sides to adhere to the agreement in good faith to ensure a peaceful political settlement, including a return to the 2004 constitution, a government of national unity and early elections.
“The vote to decriminalise a number of articles under the criminal procedure code is significant, including the possible implications for Mrs Tymoshenko. We need to see progress towards establishing a fairer and more transparent justice system in Ukraine.
“The United Kingdom will work to support these positive developments over the coming days and weeks.”