MEXICO CITY - Thousands of leftists screaming election fraud blockaded Mexico's stock market building on Thursday in a demonstration that failed to halt trading but brought tempers closer to the breaking point on the fifth day of mass protests.

Several hundred supporters of leftist presidential candidate Andres Manuel Lopez Obrador block the entrance to Mexico's stock market after others were forced to temporarily relocate portions of a sprawling protest camp following heavy rains and hail that flooded several parts of the city in Mexico City, Mexico, on Thursday, Aug. 3, 2006. Growing political unrest and drug violence are making foreigners think twice about visiting Mexico, where the $11.8 billion tourism industry is the country's third-largest legal source of income, after oil and remittances from migrants in the United States.[AP]

The exchange, a symbol of free-market economics in Mexico, stands on the elegant Reforma Boulevard that was seized on Sunday by supporters of leftist presidential candidate Andres Manuel Lopez Obrador.

About 3,000 protesters sat and lay down in front of the gleaming black dome and tower and an adjacent skyscraper housing foreign bank headquarters early on Thursday, preventing employees from entering for most of the morning.

They left around 11 a.m. (1600 GMT), jeering at workers lining up to get inside and threatening to return on Friday.

"We're leaving now. This was a show of what we can start to do," said Graco Ramirez, a senator-elect from Lopez Obrador's Party of the Democratic Revolution, or PRD.

Trading is carried out electronically and was unaffected. The market's main index slipped in early trade but was around 0.5 percent higher in afternoon trade.

Lopez Obrador is heading street protests to pressure Mexico's electoral court into ordering a full recount of votes in the July 2 presidential election he narrowly lost to conservative ruling party candidate Felipe Calderon.

Later on Thursday, he told supporters in Mexico City's historic Zocalo square that future protest action would depend on what the court decides.

"If there is no vote-by-vote recount, we are not going to permit the imposition (of Calderon as president)," he said.

Thousands of leftist protesters have seized the vast Zocalo square and Reforma Boulevard this week, causing five consecutive days of traffic chaos.

Calderon won the election with a margin of less than 1 percentage point, but Lopez Obrador claims he was the victim of massive fraud.

The electoral court has until August 31 to decide on the recount, meaning the deadlock could drag on for at least another month.

European Union observers say they found no evidence of fraud, and Calderon says his victory was clean. His lawyers say they expect at least a partial recount.

The new president will take office on Dec 1. Outgoing President Vicente Fox, whose election victory in 2000 ended seven decades of one-party rule, was barred under Mexican law from seeking re-election.

The protests have so far been peaceful, but the chaos is fueling anger in a society increasingly polarized between Lopez Obrador's mostly poor supporters and better-off Mexicans who tend to favor Calderon.

"This is an abuse," shouted a man who tried to enter the office tower adjacent to the stock exchange but was pushed away by protesters who had to be restrained by leaders pleading with them to back off.

The demonstrations have inspired some creative commuting.

As a helicopter landed on the skyscraper's roof, drawing catcalls from the crowd, Citibank pension fund salesman Ricardo Conconi, who normally drives to work from the city's more affluent south, sped by in a tourist tricycle rickshaw.

Clutching a briefcase as his panting driver pedaled, he joked about his new form of transportation: "In spite of everything, I'm getting to work more relaxed."