Pro-government lawmakers in the Ukrainian parliament on Thursday moved building and held a plenary session on different premises amid a weeks-long standoff with the opposition, which described the move as an attempted constitutional coup.
The rare walkout is the latest twist in the political tug-of-war between the Regions Party of President Viktor Yanukovych and the opposition supporting his nemesis, jailed former prime minister Yulia Tymoshenko.
The last time the Ukrainian parliament split into two and held two sessions on two different premises was under the then president Leonid Kuchma in 2000.
The ruling Regions Party said 244 deputies in the 450-seat parliament supported the move, but the opposition insists that number is just 182.
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.
On Thursday, the lawmakers, mostly from the Regions Party 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 Verkhovna Rada that has blocked parliamentary proceedings in the last days and accused the ruling party of attempting a coup.
"This is a new state emergency committee," fumed leading opposition figurehead Arseniy Yatsenyuk, referring to the failed plot to seize power from Mikhail Gorbachev in the last days of the Soviet Union in August 1991.
He accused Yanukovych of organising the walkout, which he called an attempt to seize state power, and asked prosecutors to open a criminal probe.
He warned that 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.
The ruling party insists that their session is legal since a parliamentary majority supported the move.
"We have a lot of issues that we need to solve," head of the Regions Party faction Olexander Yefremov said. "And I believe it is not entirely correct to depend on the minority."
There was no immediate reaction from Yanukovych, and his spokeswoman was unavailable.
The opposition party UDAR (Punch) headed by boxing champion Vitaly Klitschko said the ruling party and its supporters 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.
After passing 20 laws at the different premises, pro-Yanukovych lawmakers said they would go back to the old building on Friday.
"Tomorrow at 10 in the morning I will go to the plenary hall and will be persuading lawmakers to work together," parliament speaker Vladimir Rybak told journalists.
"I do not know what will be but I hope we will work."
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 Verkhovna 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.
Nationalist Svoboda (Freedom) party leader Oleg Tyagnybok called on Ukrainians to gather for a new protest in Kiev this weekend.