Yanukovych held talks with his three predecessors and the EU foreign policy chief to seek a way out of an explosive standoff with protesters, warning that opposition calls for a revolution were a threat to national security.

President Viktor Yanukovych on Tuesday held talks with his three predecessors and the EU foreign policy chief to seek a way out of an explosive standoff with protesters, warning that opposition calls for a revolution were a threat to national security.

With thousands still defying sub-freezing temperatures to protest Yanukovych's rejection of an EU pact under Russian pressure, the president met EU foreign policy supremo Catherine Ashton in Kiev, his office said.

"Substantial meeting (with) President Yanukovych, all relevant issues discussed," Ashton's spokeswoman Maja Kocijancic added on Twitter, saying the talks lasted three and a half hours but giving no further details.

In a sign of Europe's support for the demonstrators, Ashton later personally visited the epicentre of the protests on Independence Square in Kiev, an AFP correspondent said.

Yanukovych had earlier convened Ukraine's ex-leaders Leonid Kuchma, Leonid Kravchuk and Viktor Yushchenko for an unprecedented meeting at the presidential administration.

The meeting with the veteran presidents appeared to yield no immediate breakthrough, with Yanukovych issuing a warning while also trying to show signs of goodwill to the protestors.

"Calls for a revolution pose a threat to national security," Yanukovych said in comments broadcast on national television. "I want that this dark page is turned and is never allowed to happen again."

Yanukovych also said a delegation would likely be flying to Brussels to renew negotiations on key political and free trade agreements on Wednesday.

He added that Ukraine would seek to decide on the EU deals by March when it is set to hold a summit with the bloc.

Yanukovych's decision to scrap key trade and political agreements with the EU under pressure from Russia and police violence against protesters have plunged the ex-Soviet country into its most acute political crisis since the Orange Revolution in 2004.

Protests have gone into a third week, with both the authorities and the opposition showing few signs of compromise.

Police moved protesters away from government buildings Monday after a weeklong blockade but the demonstrators are still occupying Independence Square and the Kiev city hall.

Yanukovych incensed the opposition further by meeting Russian President Vladimir Putin for secret talks on Friday.

Opposition leaders said they would not negotiate with Yanukovych until he sacked the government of Prime Minister Mykola Azarov, released arrested demonstrators and punished riot police accused of crushing a protest on November 30.

Ex-presidents Kuchma and Kravchuk pointedly noted during the meeting that prime ministers had stepped down before, and indicated that Azarov could do the same.

"Civil society is now awaiting a signal from the president," said Kuchma, Ukraine's president between 1994 and 2004. Yanukovych made no public comment on the fate of the government.

In an apparent bid to placate the demonstrators, Yanukovych said that he had asked the general prosecutor to secure the release of some of the demonstrators arrested after clashes with police.

Following Yanukovych's call, the general prosecutor's office said it considered it possible to release some of the demonstrators.

Yanukovych implied the security forces bore some responsibility for violent clashes during the protests. "There are guilty on both sides," he said.

At least 10 protesters were reported injured in fresh clashes with police in the early hours of Tuesday as security forces removed barricades from around the government headquarters in the capital Kiev.

One protester suffered punctured lungs and several had broken arms or legs, a lawmaker from nationalist Svoboda (Freedom) party, Yuriy Syrotyuk, told AFP.

Police said two officers were injured as the authorities sought on Monday evening to reclaim control of the city centre and remove barricades around government buildings.

The party of jailed opposition leader Yulia Tymoshenko said Monday armed law enforcement officers had raided its headquarters, taking away documents and computer servers.

On Sunday, hundreds of thousands filled Independence Square, and dozens of masked protesters tore down a statue of Lenin.

Ukraine's Security Service opened an investigation into an alleged attempt to seize power, in an apparent bid by the state to target key opposition figures.

Several hundred were injured a week ago when a major demonstration degenerated into violence, the largest clashes in Ukraine's post-Soviet history.