Opposition candidate Henrique Capriles walked in a crowd of supporters through upscale neighborhoods in the east of Caracas during a march to celebrate International Workers' Day.
He called for an end to a government crackdown on his backers, and reiterated plans to challenge his narrow election loss in both Venezuela's court and eventually appeal to the international justice system.
He told reporters he planned to file a challenge in Venezuela's high court Thursday "in order to make use of all the institutions, all domestic remedies, because we don't have any doubt that this case will end up before the international community."
"Sooner rather than later, change will come," he said. "A better Venezuela for all will come."
In downtown Caracas, the government held its own march, featuring songs praising President Nicolas Maduro and his mentor, late president Hugo Chavez.
Both sides appeared to be trying to avoid confrontation by choosing separate locations and calling for peaceful demonstrations, although tensions were running high.
Outside the Justice Ministry, organizers set up a 30-foot-tall inflatable Chavez balloon with its fist raised in the air. Many wore red T-shirts with pro-government slogans.
"This government is defending workers' rights, increasing salaries like it should," said Juan Ramirez, a 49-year-old employee of the state telecommunications company. "Of course, there will have to be more raises to make up for inflation."
Capriles backer Claudia Sanchez, a 27-year-old office administrator, said she was marching on behalf of her brother, a government worker who she said was being pressured to participate in a pro-Maduro march.
"If they don't see him there he can fall into disgrace, he can lose his job," she said.
Many state workers have complained of intense pressure to support the government, part of what the opposition describes a broad campaign to quash dissent after Maduro's slim victory.
Tuesday night's clash erupted when members of the opposition coalition unfurled a banner in the National Assembly denouncing a ruling that strips them of most legislative powers unless they recognize Maduro's April 14 victory.
Assembly member Julio Borges appeared on an independent television station soon after Tuesday night's brawl with blood running down one side of his swollen face. The opposition said at least 17 of its allies and five pro-government deputies were injured.
Opposition lawmaker Ismael Garcia said government loyalists threw the first punches. Pro-government legislators appeared on state TV accusing opposition members of attacking them. Video showed groups of legislators shoving and pushing each other on the floor.
The opposition has refused to accept Maduro's narrow victory, saying the government's 1.49 percent margin resulted from fraud, including votes cast in the names of the thousands of dead people found on current voting rolls.
In retaliation, the government-dominated assembly has barred opposition lawmakers from public speaking and sitting on legislative committees.
Capriles is boycotting an official audit of the election and plans to file a challenge seeking to overturn it in court.
Maduro accused the opposition of provoking Tuesday's violence, which he condemned, and called on the country to work out its disputes peacefully.
National Assembly chief Diosdado Cabello has repeatedly defended barring opposition lawmakers from speaking. He said that if they don't recognize the legitimacy of the presidential election, they are casting doubt on the very system that elected them, thus losing their own legitimacy.
Opposition lawmakers have also lost their seats on legislative commissions.
Angel Alvarez, a political science professor at the Central University of Venezuela, said the brawl revealed "an escalation of the conflict between political forces" and little possibility of reconciliation in the near future.
He told The Associated Press that the political uncertainty and tension is likely to hurt Venezuela's economy, which is struggling with high inflation and frequent shortages linked to the socialist government's strict foreign exchange restrictions, price controls and nationalization of industries, including many farming and ranching businesses.
"In turbulent scenarios, barely anyone will risk investing," Alvarez said.
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