Ukraine's general prosecutor has announced that he would drop criminal charges against the activists who were detained during the three-month protest as part of an amnesty deal.

The move came hours after Ukrainian protesters vacated Kiev city hall and other municipal buildings throughout the country, 

Ukraine President Viktor Yanukovich's government had offered an amnesty deal whereby protesters had to clear all occupied municipal buildings and Kiev barricades had to be removed.

In exchange, detained activists were to be freed and criminal charges dropped.  

Ukrainian authorities provisionally freed the last 234 detained protesters under the amnesty offer and protesters vacated Kiev city hall and municipal buildings in several cities outside Kiev.

The general prosecutor's website said the law would free from criminal responsibility persons who committed crimes in relation to peaceful protest between the periods of 27 December to 2 February.

In Ivano-Frankivsk, western Ukraine, protesters vacated the regional administrative building they had occupied since 24 January. 

The unrest was sparked last November by Mr Yanukovich when he spurned a free trade agreement long in the making with the EU.

He opted for a $15 billion package of Russian credits and cheaper gas to help Ukraine's ailing economy.

At least six people have been killed in the unrest.

The Swiss ambassador in Kiev entered the building after the protesters left.

Switzerland currently holds the rotating presidency of the Organisation for Security and Cooperation in Europe, of which Ukraine is a member.

"Switzerland ... was invited by both conflicting parties to participate in the process of transferring city hall to authorities," Ambassador Christian Schoenenberger told reporters.

The move came just hours ahead of a new mass demonstration on Kiev's central Independence Square.

The square has become a sprawling, anti-government tent city barricaded off on all sides from riot police.

Today's protest is the 11th since demonstrators first rose up against Mr Yanukovych in November when he rejected a key EU pact in favour of closer ties with Russia.

The opposition had promised to prepare a mysterious "peaceful offensive" at the rally as negotiations with the government stalled.

However, the authorities yielded some ground on Friday, announcing they had freed all 234 protesters detained in the movement.

But they emphasised that charges against them would only be dropped if conditions of a recent amnesty law were met, which included the evacuation of city hall by Monday.

Some protesters have been charged with fomenting mass unrest, which carries sentences of up to 15 years in jail.