Ukraine on Monday granted amnesty to opposition protesters after they agreed to end an occupation of Kiev's city hall and other public buildings, while opposition leaders were set to meet German Chancellor Angela Merkel to ask for EU assistance.

A law dropping charges against protesters came into force a day after they vacated municipal buildings they had occupied in anger soon after President Viktor Yanukovych's November decision to reject an EU trade deal in favour of closer ties with Russia.

However nearly three months after the protests began, the opposition remains firmly entrenched in a sprawling tent city on Kiev's central Independence Square. Activists have also been allowed to continue occupying several public buildings.

The announcement that the amnesty has been granted came late Sunday after the opposition agreed to move out of municipal buildings.

"The (amnesty) law comes into force from 17 February, 2014, and stipulates that charges against people having committed offences... will be dropped," Ukrainian prosecutors said in a statement.

Yanukovych proposed the amnesty at the beginning of the month as he sought to pacify protesters following deadly clashes in Kiev in January.

"Something very important has happened. We have proved that we do not abandon our comrades in trouble," said nationalist Svoboda (Freedom) party leader Oleg Tyagnybok.

Vitali Klitschko, a former champion boxer turned opposition leader, on Monday called for the authorities to immediately amnesty activists, some of whom are still being held under house arrest.

"The authorities are still keeping hostages. That's unacceptable," he said before leaving for Germany.

Some of the protesters who had their charges lifted under the amnesty had been facing jail terms of up to 15 years.

Klitschko and Arseniy Yatsenyuk, another opposition leader, were set to meet Merkel in Berlin later Monday.

Klitschko's office said he planned to discuss "the political situation in Ukraine and the prospect of bringing in EU sanctions against representatives of the Yanukovych regime".

Klitschko was also scheduled to meet German Foreign Minister Frank-Walter Steinmeier, his office said.

"We need help. We don't need words, we need action," Yatsenyuk told tens of thousands of protesters on Independence Square on Sunday.

"We want Europe to say clearly what package of economic measures it can offer us."

The protesters had occupied Kiev city hall since December, creating an orderly headquarters with places to sleep, a first aid area and even English classes.

The opposition has also agreed to vacate part of Grushevsky Street, where riots left several dead and hundreds hurt in late January, to allow traffic to move freely.

On Sunday, an opening had been carved out in one of the street's barricades, but this was still fiercely guarded by a row of protesters in combat gear.

In the western city of Lviv, municipal workers overnight dismantled a barricade outside the city hall after protesters quit the building, the Interfax-Ukraine news agency reported.

But protesters still have a host of unmet demands, including a major reform of the constitution to reduce presidential powers in favour of the government and parliament.

Yanukovych dismissed his unpopular government after the deadly riots, but he has yet to appoint a new one and the opposition wants its members to be placed in key positions.

Ultimately, protesters want Yanukovych himself to leave, and the opposition is calling for a major rally on Tuesday in front of parliament.

Andreas Umland, a political scientist at Kyiv-Mohyla Academy in the Ukrainian capital, said the government and opposition were thought to be negotiating a form of power-sharing to be implemented before early presidential elections are held.

"For now the main question is whether Yanukovych will agree to power-sharing, what kind of power-sharing and how much power will be left to the office of the president," he said.