Ukrainian President Viktor Yanukovych refused to step down Saturday and denounced a "coup" by protesters as the emboldened opposition took control of parliament and parts of Kiev in another dramatic turn in the three-month crisis.

Yanukovych's regime appeared close to collapse as protesters took control of his offices and lawmakers voted to immediately free jailed pro-Western opposition icon Yulia Tymoshenko.

But Yanukovych defiantly told a local television station in the eastern Ukrainian city of Kharkiv -- a pro-Russian bedrock of support -- that he would fight tooth and nail against the "bandits" trying to oust him.

"I am not leaving the country for anywhere. I do not intend to resign. I am the legitimately elected president," the 63-year-old leader said in a firm voice.

Yanukovych said with a hint of outrage that "everything happening today can primarily be described as vandalism, banditry and a coup d'etat."

"This is not an opposition," Yanukovych scoffed. "These are bandits."

Yet a sense of an emerging power vacuum gripped the charred heart of the capital a day after Yanukovych 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.

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

"We have taken the perimeter of the president's residence under our control for security reasons," Mykola Velichkovich of the opposition's self-declared Independence Square defence unit told AFP.

Thousands of mourners meanwhile brought carnations and roses to dozens of spots across Kiev's iconic Independence Square on which protesters were shot dead by police in a week of carnage that claimed nearly 100 lives.

Coffins draped with Ukraine's blue-and-yellow passed from shoulder to shoulder through the crowd before being taken outside the city for burial.

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

The country's vast army issued its own statement hours later vitally stressing that it "will in no way become involved in the political conflict."

The next test for the police will come Sunday when a deadline expires for protesters to relinquish public spaces such as Independence Square -- the focal point of unrest that Yanukovych sparked in November by ditching an historic 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 against Western efforts to bring the economically struggling nation of 46 million into their fold.

Russia's foreign ministry on Saturday accused the opposition of "submitting itself to armed extremists and looters whose actions pose a direct threat to the sovereignty and constitutional order of Ukraine."

The deal on Friday called for early presidential elections to be held by December and a unity government to be set up.

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

"We must, as the people demand, adopt a resolution calling on Yanukovych to immediately resign," boxer turned opposition leader Vitali Klitschko told deputies in Ukraine's Verhovna Rada parliament.

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

Deputies also voted to immediately release Tymoshenko -- a fiery and polarising former prime minister who is serving a seven-year jail sentence for "abuse of power" she controversially received after her arch-foe Yanukovych took office in 2010.

But Yanukovych called the flurry of opposition-backed laws passed by parliament since Friday "illegitimate".

"They must hear this from me -- I do not intend to sign anything," Yanukovych said in the television address.

Yet the ruling Regions Party that had previously pushed Ukraine closer toward Russia was standing in disarray on Saturday amid mass defections by lawmakers to opposition ranks.

More than 40 lawmakers have already quit the Regions Party -- once in control of 208 votes in the 450-seat Rada -- since the deadly unrest first erupted on Tuesday.

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

Deputies also named another Tymoshenko ally, Arsen Avakov, as interior minister in place of Vitaliy Zakharchenko -- a hate figure in the opposition who is blamed for ordering the police to open fire on unarmed protesters.

Anti-Russian sentiment has in recent weeks been sweeping the parts of Ukraine that until recently had been strongly loyal to the Kremlin and wary of the cultural values espoused by EU states.

Ukrainian media reported that protesters had since Friday been toppling statues of Lenin -- the Soviet founder who for decades has symbolised Moscow's political might -- in the pro-Russian cities of Dnipropetrovsk and Potava.