Ukraine's parliament voted Sunday to temporarily hand the country's presidential powers to a top official, a day after former leader Viktor Yankovych -- whose whereabouts are unknown -- was ousted following a week of deadly protests.

A plane with Yanukovych onboard was denied permission to take off Saturday evening from Donetsk, a city in eastern Ukraine that is the president's base of support, the State Border Guard Service said. Oleh Slobodyan of the State Border Guard service told the Associated Press Sunday that the plane did not have the proper documentation. It is not clear what the plane's ultimate destination would have been. The president was driven off in a car from the airport.

Yanukovych did speak on television Saturday in the city of Kharkiv, near the border with Russia, accusing his opponents of trying to overthrow the government.

"Everything that is happening today is, to a greater degree, vandalism and banditry and a coup d'etat," he said. "I will do everything to protect my country from breakup, to stop bloodshed."

However, Yanukovych's movements have not been accounted for since, and even his spokesman told the Associated Press Sunday morning that he does not know where his boss is.

The parliament, in a special session Sunday, voted overwhelmingly to temporarily hand Yanukovych's president's powers to speaker Oleksandr Turchinov, a top ally of former Ukrainian Prime Minister Yulia Tymoshenko.

The legislators also voted to replace a string of government ministers.

The legitimacy of the parliament's flurry of decisions in recent days is under question. The votes are based on a decision Friday to return to a 10-year-old constitution that grants parliament greater powers. Yanukovych has not signed that decision into law, and he said Saturday that the parliament is now acting illegally.

However, legal experts said that de facto the parliament is now in charge.

Ihor Koliushko, head of the Center for Political and Legal Reform, said that given the president's absence from Kiev and the exceptional situation, "I think it would be right to say that we don't have a head of the state, but the president's duties are being carried out ... by the head of the Verkhovna Rada," or parliament.

Meanwhile, thousands of curious and contemptuous Ukrainians roamed the suddenly open grounds of the lavish compound outside Kiev where Yanukovych was believed to live.

The Kiev protest camp at the center of the anti-Yanukovych movement was calm but still full of dedicated demonstrators Sunday morning. Protester self-defense units who have taken control of the capital peacefully changed shifts Sunday. Helmeted and wearing makeshift shields, they have replaced police guarding the president's administration and parliament, and have sought to stop radical forces from inflicting damage or unleashing violence.

Ukraine is deeply divided between eastern regions that are largely pro-Russian and western areas that widely detest Yanukovych and long for closer ties with the European Union. Yanukovych's shelving of an agreement with the EU in November set off the wave of protests, but they quickly expanded their grievances to corruption, human rights abuses and calls for Yanukovych's resignation.

The political crisis in the nation of 46 million has changed with blinding speed repeatedly in the past week. First there were signs that tensions were easing, followed by horrifying violence and then a deal signed under Western pressure that aimed to resolve the conflict but left the unity of the country in question.

Tensions mounted in Crimea Sunday, where pro-Russian politicians are organizing rallies and forming protest units and have been demanding autonomy from Kiev. Russia maintains a big naval base in Crimea that has tangled relations between the countries for two decades.

Parliament has also voted to set elections for May 25. But Yanukovych said in the televised address that he now regards the parliament as illegitimate and he won't respect its decisions.

Tymoshenko, the long-jailed blond-braided heroine of Ukraine's 2004 Orange Revolution, left imprisonment on Saturday after the Ukrainian parliament voted to decriminalize the charge on which she was convicted.

She increasingly appears to have the upper hand in the political battle as to who will be the next leader of Ukraine, winning the backing Sunday of a leading Russian lawmaker and congratulations from German Chancellor Angela Merkel and U.S. senators on her release.

Tymoshenko's name circulated Sunday as a possibility for acting prime minister pending May 25 presidential elections, but she issued a statement via her party Sunday asking her supporters not to nominate her for the position.

She may want to focus her energies instead on campaigning for president and building up strength after her imprisonment. She spoke to an excited crowd of about 50,000 in Kievâ€™s Independence Square Saturday night from a wheelchair because of a back problem aggravated during imprisonment, her voice cracked and her face careworn.

"You are heroes, you are the best thing in Ukraine!" she said of the victims.

And she urged the demonstrators not to yield their encampment in the square, known in Ukrainian as the Maidan.

"In no case do you have the right to leave the Maidan until you have concluded everything that you planned to do," she said.

"We missed Yulia and her fire so much," said demonstrator Yuliya Sulchanik. Minutes after her release, Tymoshenko said she plans to run for president, and Sulchanik said "Yulia will be the next president -- she deserves it."

Russian legislator Leonid Slutsky said Sunday that naming Tymoshenko prime minister "would be useful for stabilizing" tensions in Ukraine, according to Russian news agencies.

Russia's finance minister on Sunday also urged Ukraine to seek a loan from the International Monetary Fund to avoid an imminent default. Russia in December offered Ukraine a $15 billion bailout, but so far has provided only $3 billion, freezing further disbursements pending the outcome of the ongoing political crisis.

Yanukovych's authority in Kiev appeared to be eroding by the hour and suspicions mounted that he was trying to get out of the country. His support base crumbled further as a leading governor and a mayor from the eastern city of Kharkiv fled to Russia.

The conviction of Tymoshenko was one of the underlying issues driving the protests.

After the 2004 Orange Revolution helped bring Viktor Yushchenko to the presidency, Tymoshenko became prime minister. But when Yanukovych won the 2010 election, Tymoshenko was arrested and put on trial for abuse of office, an action widely seen as political revenge.

EU foreign affairs chief Catherine Ashton welcomed the release of Tymoshenko as "an important step forward in view of addressing concerns regarding selective justice in the country."

Russia came out Saturday firmly against the peace deal, saying the opposition isn't holding up its end of the agreement, which calls for protesters to surrender arms and abandon their tent camps. Tymoshenko's entreaty is likely to make the latter condition slow to be fulfilled.

European officials urged calm. Ukraine's defense and military officials also called for Ukrainians to stay peaceful but did not clearly come on the side of the president or opposition.

The past week has seen the worst violence in Ukraine since the breakup of the Soviet Union a quarter-century ago. At Independence Square Saturday, protesters heaped flowers on the coffins of the dead.

The Health Ministry said the death toll in clashes between protesters and police that included sniper attacks had reached 82 over the last week. The protesters put that figure at over 100.

The Associated Press contributed to this report.