Members of Venezuela's National Assembly say post-election tensions set off a brawl between politicians that left one opposition assembly member badly bruised and bleeding.
Video from inside the National Assembly showed opposition politicians unfurling a banner and then a fight breaking out between legislators.
The fracas came after the government-controlled Assembly passed a measure denying opposition members the right to speak in the chamber until they publicly recognised Nicolas Maduro as the nation's president.
The opposition has refused to accept President Maduro's narrow 14 April victory, prompting the pro-government side to try to bar them from the assembly.
Mr Maduro, who was late socialist leader Hugo Chavez's chosen successor, defeated opposition candidate Henrique Capriles by 1.5 percentage points.
Both sides accused each other of starting the incident, which took place behind closed doors without media present.
Opposition assembly member Ismael Garcia said legislators threw punches after members of his coalition tried to protest a proposal barring them from legislative activities.
Assembly member Julio Borges appeared on an independent television station with blood running down one side of his swollen face.
Mr Borges said he blamed President of the National Assembly Diosdado Cabello for the fight.
"The responsibility lies directly with Diosdado Cabello who embodies the hate, repression, the fascism that he wants to accuse the rest of the country of and who doesn't recognise what's nothing more than a repression of our country on 14 April," he said.
President Maduro responded to the brawl by saying that the opposition was there to provoke a fight.
"They tell us that, and we knew, that the opposition came to provoke violence and there was a fierce exchange of blows," he said."We have to pursue peace, coexistence, respect for the constitution, laws, ideas and tolerance," Mr Maduro told the audience to applause.