After days of growing protests in the Ukrainian capital, Kiev, the speaker of parliament, Vlodymyr Rybak, says discussions between the government and opposition will begin on Monday.
Mr Rybak appeared on national television after protesters occupied the city hall in Kiev in the biggest demonstration yet against the pro-Moscow president, Viktor Yanukovych, since he backed out of an agreement bringing the country closer to the European Union.
Vast crowds rallied on Kiev's Independence Square, defying a ban imposed a day earlier. Estimates of the numbers ranged from around 100,000 to more than 350,000, the BBC reports.
Opposition leaders also occupied a trade union building, turning it into a temporary headquarters, on Sunday.
Police used tear gas and stun grenades to repel a group of protesters advancing on police lines and throwing large stones.
The protests started more than a week ago. Mr Yanukovych argued that Ukraine could not afford to sacrifice trade with Russia, which opposed the deal.