KIEV: Ukraine's opposition vowed Sunday to defy a sudden ban on protests in central Kiev and rally in support of early elections after President Viktor Yanukovych rejected a historic EU pact.

The ex-Soviet nation of 46 million was thrown into its deepest crisis since the 2004 pro-democracy Orange Revolution after Yanukovych snubbed EU leaders at a Vilnius summit and opted to keep Ukraine aligned with its former master Russia.

The government's decision -- first announced a week before Friday's EU meeting -- sparked mass demonstrations that turned violent in the early hours on Saturday when hundreds of rubber baton-wielding police drove about 1,000 protesters off Kiev's focal Independence Square.

The demonstrators took shelter at the nearby Mikhailovsky Monastery as they planned their next move.

About 500 of them spent the night on Mikhailovsky Square burning wood in metal barrels to ward off the freezing temperature and receiving food from the monastery's monks.

Opposition parties have vowed to form a “national resistance task force”and call for early elections as well as a countrywide strike that includes daily rallies aimed at blocking the entrance to the Ukrainian government seat in Kiev.

The Ukrainian parliament's opposition leader Arseniy Yatsenkyuk also promised to lead protesters Sunday on “a peaceful march to the heart of the Ukrainian capital -- on Independence Square,”

But there were fears that Sunday's demonstration could turn violent after Kiev's main administrative court issued a full ban on protests on Independence Square and its surrounding streets.

“The court granted a judgement in favour of the Kiev mayor's office,” rally organisers' attorney Yevgeniya Zakrevskaya told AFP.

“Mass demonstrations are banned through January 7, 2014.”

Western outrage

The police crackdown on protesters sparked a new round of Western condemnation of the Ukrainian government but was met with notable silence by Russian President Vladimir Putin's Kremlin.

US State Department spokeswoman Jen Psaki called on Kiev authorities to respect Ukrainians' right to free expression and assembly.

“These are fundamental to a healthy democracy and the respect for universal values on which the United States' partnership with Ukraine depends,” State Department spokeswoman Jen Psaki said.

“Violence and intimidation should have no place in today's Ukraine.” Ukraine's leaders appeared to take steps Saturday to distance themselves from the violence by announcing the launch of a formal probe that would identify and punish those responsible for sparking the unrest.

Yanukovych said a statement that he was “deeply outraged by events that took place on Independence Square overnight.””I condemn the actions which led to a confrontation and people suffering,” he added.

The Ukrainian leader also reaffirmed his longer-term commitment to closer EU relations, saying that “we are united in the choice of our common European future.”Ukrainian Prime Minister Mykola Azarov said he could not immediately tell whether the riot officers' use of force was appropriate.

Opposition demands

Jailed former prime minister Yulia Tymoshenko -- a top Yanukovych rival whose release was a condition for signing the EU deal -- called on Ukrainians to press ahead with their fight.

“I am calling on all of Ukraine's mothers and fathers not to leave the authorities' actions unanswered,” she said in a statement read out by her daughter Yevgenia to about 10,000 supporters on Mikhailovsky Square.

World boxing champion turned opposition lawmaker Vitali Klitschko also told the Ukrainian flag-waving crowd that “we can and should remove these authorities.””We call on citizens to come out on the streets and peacefully express their position,” he added in a statement issued by his office Sunday.

The opposition has drawn up a list of tough demands that includes the immediate ouster of both Yanukovych and his government as well as early parliamentary elections.

Yatsenkyuk has also called on supporters to blockade the Ukrainian government building when it resumes work on Monday.

The new “national resistance task force” meanwhile was aimed at organising an indefinite nationwide strike. Church leaders in the deeply religious country have condemned the violence and called on both the authorities and the opposition to avoid further clashes.