The regime of Ukraine's president appeared close to collapse as the emboldened opposition took control of central Kiev and key government and parliament positions and voted to immediately free jailed opposition leader Yulia Tymoshenko.

An emerging power vacuum gripped the charred heart of the capital, Kiev, a day after Viktor Yanukovich and his political rivals signed a Western-brokered peace deal to end the ex-Soviet nation's worst crisis since independence from Moscow in 1991.

Yanukovich, who left the capital on Friday night, is thought to have travelled to eastern Ukraine, his power base.

Boxer turned Ukrainian opposition leader Vitali Klitschko earlier said that Yanukovich had left Kiev and that the country must hold early elections.

Anti-government demonstrators entered Yanukovich's compound in the capital on Saturday and were controlling the entrance, a Reuters news agency journalist at the scene reported.

Key government buildings were without police protection and baton-armed protesters dressed in military fatigues wandered freely across the president's once-fortified compound.

The Ukrainian police appeared to retreat from their entrenched defence of the pro-Russian government by releasing a statement in support of "the people" and "rapid change".

"The police is at the service of the people and completely shares its aspirations for rapid changes," the interior ministry said in a statement.

"We pay homage to the dead."

Deadline expiry

The next test for the police will come on Sunday when a deadline expires for protesters to relinquish public spaces such as Independence Square - the focal point of unrest that Yanukovich sparked in November by ditching an EU agreement in favour of closer ties with old master Moscow.

The Ukrainian protests have escalated into a Cold War-style confrontation pitting attempts by the Kremlin to keep reins on its historic fiefdom and Western efforts to bring the economically struggling nation of 46 million into their fold.

The deal on Friday called for the holding of early presidential elections by December and a forming of a unity government.

But signs of the authorities' slipping grip on power were heightened by a bold push by parliament leaders to force Yanukovich to stand down immediately and to immediately free the jailed Tymoshenko.

The parliament has made several important political appointments - including a new parliamentary speaker, interior minister in charge of the nation's police and a Prosecutor General.

They have also voted to speed up the release of jailed opposition leader Yulia Tymoshenko, who is serving a seven-year jail sentence for "abuse of power".

But there have been conflicting reports regarding her release.

"We must, as the people demand, adopt a resolution calling on Yanukovich to immediately resign," Klitschko told deputies in Ukraine's Verhovna Rada parliament.

He called for presidential elections to be held by May 25 and said the parliament was Ukraine's "only legitimate body of power."

The president's ruling Regions Party that had previously pushed Ukraine closer toward Russia was also standing in disarray Saturday amid mass defections by lawmakers to opposition ranks.

Parliament speaker Volodymyr Rybak resigned in favour of Tymoshenko's right-hand man Oleksandr Turchynov.

Meanwhile, governors and regional legislators from Russian-speaking eastern Ukraine have questioned authority of national parliament, according to AP.