Venezuela opposition leader Henrique Capriles announced Wednesday he would formally contest results from last month's presidential poll, as both sides held rival May Day rallies in Caracas.
Capriles told supporters at his demonstration in eastern Caracas that the formal challenge would be presented to the Supreme Court on Thursday. He had been under a Monday deadline if he wanted to file with the top court.
"We are going to exhaust all the internal fora because we have no doubt that this case is going to wind up before the international community. This case is going to end up going to every country where there is a democracy," Capriles said.
Tensions have heated up in the country since the April 14 vote, which official results gave to Nicolas Maduro, the late leftist firebrand Hugo Chavez's hand-picked successor, by a 1.5 percent margin.
Capriles, who has accused Maduro of stealing the election, has rejected an audit of the vote by the National Electoral Council, begun Monday, as a "farce" after it refused to include physical voting records in the review.
The council has limited itself to a narrow, technical review of the electronic voting system while insisting that no audit can reverse Maduro's win.
Maduro led a rival march in central and western Caracas -- a last minute route change to avoid a confrontation with opposition marchers, who chose a major road in the east of the capital for their demonstration.
They came a day after a brawl broke out in the National Assembly over the pro-Chavez majority's refusal to grant the opposition the right to speak until they recognized Maduro as the legitimate winner.
The United States said it was "very concerned" about the development, with State Department spokesman Patrick Ventrell expressing "solidarity with those injured."
"Let me speak clearly: violence has no place in a representative, democratic system and is particularly inappropriate within a National Assembly," Ventrell said.
Opposition politician Julio Borges said Tuesday night he was beaten by ruling party members, and he was "not the only one." Videos released by opposition deputies showed the lawmakers coming to blows.
Borges said the ruling party majority had voted to deny opposition lawmakers their right to speak because they have not recognized Maduro's election.
Chavista deputy Elvis Amoroso defended his colleagues Wednesday, saying if opposition lawmakers "do not recognize our constitutional president, then we do not need to recognize them, since they were also elected under the same voting system."
At Maduro's rally Wednesday, Zoraida Castro, 59, also blamed the opposition.
"Due to their provocations (from the right), there is a tense atmosphere, because there is one sector that doesn't recognize Maduro and another that defends him," she told AFP.
Across town at Capriles' rally, emotions were equally high.
"I'm in this march because of the discontent we are living in the country, for the dud elections. I feel my vote was stolen," said Sara Clavico, 60, who works for the opposition-party mayor in the municipality of Chacao.