BUENOS AIRES -- Even by the standards of Argentina, where people like to joke that soccer is less a pastime than a pathology, a recent surge of fan violence has been exceptional.

In the past two weeks, local stadiums have erupted in mass fights -- some of them all-out brawls injuring dozens of fans -- an average of every other day.

Politicians are vowing reforms, and most fans and league officials are blaming the violence on organized hooligan groups known as barrabravas, which are increasingly labeled as out-of-control mafias eroding the integrity of the sport.

On Tuesday afternoon, as police fired rubber bullets into a crowd to separate warring fans in a Buenos Aires suburb, a congressional committee was grilling the president of River Plate, one of South America's most famous soccer clubs, about the violence that has resulted in the closure of its 65,000-seat stadium for five games.

Among the incidents in question was a gun-and-knife fight Feb. 11 among members of a River Plate hooligan gang that sent picnicking families fleeing the stadium.

River Plate officials eventually expelled six fans known to be affiliated with the barrabrava. But the incident sparked a public backlash against such gangs, many of which are rumored to receive money, tickets and jobs from the clubs. Club officials customarily deny links to the barrabravas. Many hooligan leaders, even those widely known to belong to specific gangs, often treat their affiliations as badly kept secrets: They shun media exposure and publicly deny connections to specific acts of violence as well as links to the clubs. But almost everyone else connected to the sport -- from security officials down to the most casual of fans -- simply assumes that the hooligan gangs and the clubs they cheer for are closely connected.

"The barrabravas are a cancer," said Hernán Fernández, 30, a River Plate fan standing outside the stadium one evening this week to protest its closure. "They have been a problem for a long time, but now they are stronger than ever, and the problems are getting worse."

According to local security officials, the gangs -- which began in Argentina in the 1950s -- have begun exporting their methods. Javier Alberto Castrilli, an official with Argentina's Interior Ministry who is in charge of soccer security, said the barrabravas' influence has spread in the past five years across South America and into Mexico.

"Here in South America, in countries where five years ago you'd never be able to imagine that so much soccer-related violence could exist . . . organization among barrabravas has reached very highly developed levels," Castrilli, a former World Cup referee, said in an interview Tuesday. "Groups abroad are copying the chants, the songs and even the flags that got their start here in Argentina."

According to a report this week in Olé, an Argentine daily newspaper devoted to soccer, leaders of some of the country's major barrabravas have shared their methods with fan groups in countries including Colombia and Mexico, charging money for courses in how to extort from team officials, use weapons and generally wreak havoc. The article quoted Rafael Di Zeo, considered a leader of a barrabrava of the Boca Juniors club, as saying that groups such as his are considered "the Harvard" of hooligans worldwide. "They come here to learn," Di Zeo said, according to the article.

Whether connected to the Argentine gangs or not, fan-related violence has spiraled throughout the region this year. In Colombia last week, police broke up fights between rival fan groups, according to the Associated Press. In Mexico, officials outlawed the free distribution of tickets to unruly fan clubs. In Peru, 10 people were injured by flying debris during a club match. In Chile, officials suspended two university matches, citing inadequate security.

South America has no monopoly on fan violence, however. This week, French police used tear gas to dampen passions at a Champions League match between Lille and Manchester United. In Italy this month, soccer games were suspended after a police officer was killed during a riot. And German officials canceled matches last weekend after fans attacked 300 police officers outside a stadium in Saxony on Feb. 10.

In Argentina, officials say they hope legislative measures can stem the influence of the hooligan groups. Castrilli and Interior Minister Aníbal Fernandez have sponsored a bill that would give judges more power to stop hooligan leaders from entering stadiums. They have also suggested that the stadiums need better security measures, such as more video and audio surveillance devices.

"These stadiums were designed 60 or 70 years ago, when the public wore ties to soccer matches," Castrilli said. "It's a different world now."

Castrilli said the current problems stem from the culture of leniency and neglect that ruled Argentine soccer in the 1980s, when the barrabravas amassed power. But even in recent years, threats of crackdowns have had little effect. In the late '90s, then-President Carlos Menem issued executive orders to prevent known hooligans from entering stadiums, but most clubs ignored them.

River Plate's president, José María Aguilar, testifying before the National Congress this week, said he maintained absolutely no relations with the group linked to last week's violence. He denied reports that the club pays the groups thousands of dollars each month and supplies them with free tickets.

But Aguilar added that expelling fans believed to be leaders of the barrabravas would probably do little to stem soccer violence because the hooligan groups have acquired too much cultural influence. He said that one of the hooligan leaders he expelled from River Plate this week, for example, signs as many autographs as the team's star midfielder.

"The attraction that they hold for the middle class, which includes the majority of the public, is something inexplicable," Aguilar said.