The pro-government majority in the Ukrainian parliament on Thursday moved building and held a plenary session on different premises amid a weeks-long standoff with the opposition.
The lawmakers, mostly from the ruling Party of Regions and their Communist Party backers, moved into a building located a block down from the Verkhovna Rada parliament in central Kiev.
Meanwhile, opposition deputies kept up a blockade in the 450-seat Verkhovna Rada that has blocked parliamentary business in the last days.
The Regions Party says 244 lawmakers moved out, while the opposition insists that number is much lower.
The rare walkout is the latest twist in the weeks-long tug-of-war between the Regions Party of President Viktor Yanukovych and the opposition supporting his nemesis, jailed former prime minister Yulia Tymoshenko.
The opposition has sought to disrupt parliamentary proceedings by blockading the speaker's rostrum, and the parliament has held only a few full-blown sessions over the past few weeks.
Leading opposition figurehead Arseniy Yatsenyuk warned any decisions taken during the extramural session would not be legal.
"Any decisions taken by the ruling party supporters in the backstreets are unconstitutional," he was quoted as saying in a statement.
"And any attempts to take such decisions are attempts to seize state power and an infringement on the Ukrainian Constitution and the consitutional order."
The opposition party UDAR (Punch) headed by boxing champion Vitaly Klitschko said the majority did not allow the opposition deputies to join the rest of the legislature by blockading the entrance to the plenary hall.
"We are sure they do not have 244 deputies there. The Regions Party is lying to the people again," party member Vitaly Kovalchuk was quoted as saying in a statement.
Earlier this week Yatsenyuk and Klitschko led over 5,000 opposition protesters on a march through central Kiev in what was the biggest protest action in the Ukrainian capital this year.
Among other demands, the opposition wants the authorities to schedule a date for new Kiev mayoral elections which they would have a chance of winning in a major reverse for Yanukovych.
The opposition wants the elections to take place in early June but the Rada has so far failed to confirm this.
Kiev's previous mayor Leonid Chernovetsky stepped down last year and the city has been run by a city manager, Olexander Popov, appointed by Yanukovych in 2010.
Chernovetsky had effectively failed to carry out his duties for several years after bewildering Ukrainians with his eccentric antics which led opponents to accuse him of mental instability.