BUENOS AIRES, Argentina -- The soccer field is surrounded by a moat, a concrete wall topped by iron spikes and several snarling German shepherd guard dogs.
There are 20-foot-high fences with barbed wire separating gangs of opposing fans, and dozens of police officers armed with pistols separating the gangs from the more civilized spectators.
Police frisk fans for weapons at the entrance to the stadium. And players enter the field through a huge rubber tunnel to protect them from stones, coins, food, radio batteries and other objects thrown by spectators.
Outside the stadium, a water cannon mounted on an armored personnel carrier stands ready, along with dozens of armed police with tear gas. Many police wear riot gear and some are on horseback.
It is a muggy Sunday at La Bombonera Stadium, home of Boca Juniors, one of Argentina's best soccer teams, and perhaps this country's most violent fans.
More than 100 people have been killed at soccer matches in Argentina in the last four decades, many of them here in La Boca, a tough, working-class Italian neighborhood of cobblestone streets and run-down, tin-and-concrete houses.
Most were killed or maimed by soccer gangs, called Barras Bravas, who attack fans from opposing teams, or people they just don't like. In the last few years, a stray bullet killed a boy at a Boca game, a flare shot through the neck killed another fan and a 120-pound piece of iron railing thrown from the upper deck crushed another fan in December.
The December killing outraged Argentine President Carlos Menem, who ordered officials from Boca's soccer club and other major teams to try to prohibit soccer gangs from entering the stadiums. Yet, though fewer incidents of violence have taken place this year, most fans remain fearful.
"This is the most dangerous stadium in the world. You have to be very careful," said Julian Figueroa, 32, a longtime soccer fan, as he waited cautiously in a ticket line, recounting how he narrowly escaped being beaten by a crowd of Boca fans three years ago.
Nearby, men and their sons dressed in the blue-and-yellow jerseys of the home team walked hand in hand toward the entrances. There were old men, alone, shuffling forward, and groups of impoverished youngsters in torn shorts.
The crowd was distinctly working-class, mostly port or factory workers of Italian and Spanish decent. Women and rich Argentines generally don't go to soccer matches -- they prefer polo -- and if they do, they leave their jewelry, watches and fancy clothes at home. Too many thieves.
Mostly, there were surging crowds of shirtless young toughs waiting for something to happen. They pushed their way through the lines, some of them shouting, and made their way to the Popular section, the cheap seats that are the home turf for gang members.
On this Sunday, Boca was playing Independiente, a longtime rival and a favorite to win the Argentine championship. Opposing fans hate each other with a passion that appears unequaled in American sports -- and often has little to do with sports.
"Most of these youths come to the games to let off steam. They are poor. They have no work. They are extremely frustrated," said Eric Weil, sports editor at the Buenos Aires Herald, an English-language daily.
"Football [soccer] violence is a problem in Europe. It's a problem in the rest of South America. But it's been out of control here."
Weil blames club officials in part for inciting the violence, saying they encourage the formation of gangs by giving them free tickets, free transportation to games and other goodies in return for acting as their muscle.
"If club officials want to get rid of a coach, they tell the gangs to lean on them. There have been death threats. In one incident, a coach's daughter was attacked," he said.
The Popular sections were packed two hours before kickoff, with fans waving banners and shirts, shaking fists and screaming songs -- many clever, many obscene -- about the teams.
The only calm was on the lime-green field, separated from the vTC crowds by the walls and the fences and the guard dogs and the moat, which carries the warning: "Don't cross. It could endanger your life."
The scene was from another age, as one would imagine the Romans and their gladiators, and when the players arrived -- by this time all 50,000 seats were full -- the spectators showered the field with confetti and rolls of paper, letting out deafening roars.
The game began at 5 p.m. It was graceful at first, almost like a ballet, with the spectators' chants acting as a sort of narration.
But it was almost like watching a game on television with no sound. There was no public-address announcer, and the real action was away from the field.
Opposing gangs of fans continued chanting and singing. They stood the entire game, often jumping up and down together in a way that made them appear as a single live organism. The sharp sound of firecrackers punctuated the roar of the crowd.
"I am a fanatic. I have been to every game for 20 years," said Eduardo Santino, 37, who was sitting in the Boca section with his son. "If we didn't have football, we wouldn't have anything."
Santino's 62-year-old father was in another section of the stadium, but his wife and daughter stopped going to the games last year. They witnessed a huge brawl and are scared.
"It's violent, and sometimes frightening," Santino said. "They hate us and we hate them. It's just the way it is. It's history."
Juan Simon, Boca's star fullback and a starter on the Argentine national team that placed second in the 1990 World Cup, said football in his country is "a religion."
"Argentines are passionate people, and there is nothing they are more passionate about than football. I don't know why," said Simon, who played several years in France before returning to Boca two years ago.
Halftime passed -- the score was 0-0 -- and the chanting and singing continued. Fans sitting in the upper deck began pouring urine on fans sitting below them. The fans below complained to police, chanting, "Do something, you sons of a. . . ." The police didn't move.
In the second half, the mood of the fans turned increasingly sour. There were few shots on goal, and fans whistled in disgust at the players, who were tiring.
The game would end in a tie, with Boca remaining in first place and Independiente not far behind.
There were no controversial calls, which often spark after-the-game riots, and most fans filed out of the stadium with little rancor, just the usual ranting and raving about what this player or that player should have done.
The streets outside were almost dark. Groups of shirtless teen-agers with tattoos drank beer on the sidewalks, and old men and women stood on their balconies watching the fans move quietly through their neighborhood.
A lone police siren punctuated the night.