(KIEV) - Ukrainian President Viktor Yanukovych on Monday agreed to scrap anti-protest laws but said jailed demonstrators would be released only if barricades are taken down -- on the eve of a key EU-Russia summit in Brussels.

Opposition leader Arseniy Yatsenyuk also formally turned down the post of prime minister, held out by Yanukovych following a previous round of negotiations on Saturday, the presidency said in a statement on fresh talks with the opposition.

"There was a political decision to abolish the January 16 laws that have caused so much discussion," read the statement, which comes on the eve of a special parliament session that is due to discuss possible measures aimed at ending the deadly two-month crisis.

"Yatsenyuk declined to lead the government of Ukraine," it added.

Russian President Vladimir Putin is on Tuesday due in Brussels, after which the European Union's foreign policy chief Catherine Ashton will travel to Kiev in a diplomatic flurry reflecting growing international concern.

Yanukovych met with the three main opposition leaders -- Yastenyuk, former boxing champion Vitali Klitschko and nationalist Oleg Tyagnybok -- who have called for a new mass demonstration on Tuesday on Independence Square, the Maidan.

Radical protesters earlier on Monday agreed to leave the premises of the justice ministry building they had stormed on Sunday evening.

The protests began in November as a drive for EU integration after Yanukovych ditched a key deal with the bloc under Russian pressure, but have now turned into a drive to unseat him.

At least three protesters have been killed in clashes with the security forces and the protests have spread far beyond their hub in Kiev to outlying regions, including Yanukovych's heartland in eastern Ukraine.

Under unprecedented pressure, Yanukovych on Saturday had offered to give the opposition posts in government and to make changes to the constitution that would reduce the powers of the presidency and boost the government.

Opposition to press ahead with protests

But opposition leaders have said they will press ahead with their protests until all their demands are met -- including early elections.

Taking a more radical line than many in the opposition, the jailed leader of the 2004 Orange Revolution, Yulia Tymoshenko, earlier urged opposition leaders to reject the "humiliating terms" set by the presidency.

Klitschko, who was offered the job of deputy prime minister, had already dismissed it as "a poisonous offer" aimed at driving a wedge between the leaders of the demonstrations.

Amid a febrile atmosphere in Kiev, the Dzerkalo Tyzhnia news website reported the cabinet was preparing a state of emergency decree that would restrict movement on some Kiev streets.

But Foreign Minister Leonid Kozhara told reporters Monday: "Today we are not considering the introduction of a state of emergency. Today, this measure is not on the table."

US Vice President Joe Biden called Yanukovych on Monday and warned him that "declaring a state of emergency or enacting other harsh security measures would further inflame the situation and close the space for a peaceful resolution," according to a White House statement.

Dzerkalo Tyzhnia also reported that the government was planning to hugely expand the Berkut riot police force blamed for much of the violence in Kiev six-fold to 30,000 people.

In his phone call to the president, Biden urged him to pull back the riot police and work with the opposition on de-escalating the crisis.

Tensions remained high in Kiev after several dozen radical protesters seized control of the justice ministry. After occupying the premises for more than 12 hours, the activists walked out of the building though dozens dressed in battle fatigues still blocked the front entrance.

Protesters now control much of the centre of Kiev around a hub on Independence Square, with their camp protected by barricades several metres high and guarded by activists in balaclavas armed with baseball bats.

They also occupy regional government offices in all but one region in the west of the country, with local opposition lawmakers and militants uniting to run their regions.

Protesters now occupy or are blockading a total of 10 of the 25 regional centres across Ukraine.

Security forces appear to have been fighting back in the east, using force to disperse protests in the regional centres of Dnipropetrovsk, Cherkasy and Sumy and arresting dozens, local media reported.

The escalating crisis is expected to dominate the meeting between Putin and European Council president Herman Van Rompuy and European Commission head Jose Manuel Barroso.

Moscow has criticised protesters as extremists, with Foreign Minister Sergei Lavrov condemning "fascistic youth" and warning against external interference.

But the West has voiced concern about police violence, and says Ukrainians' right to protest should be protected.