A bloody conflict between Hispanic and black gangs is spreading across Los Angeles. Hundreds are dying as whole districts face the threat of ethnic cleansing. Paul Harris reports from the epicentre of America's new urban warfare

Father Greg Boyle keeps a grim count of the young gang members he has buried. Number 151 was Jonathan Hurtado, 18 - fresh out of jail. Now the kindly, bearded Jesuit mourns him. 'The day he got out I found him a job. He never missed a day. He was doing really well,' Boyle says.

But Hurtado made a mistake: he went back to his old neighbourhood in east Los Angeles. While sitting in a park, Hurtado was approached by a man on a bike who said to him: 'Hey, homie, what's up?' He then shot Hurtado four times. 'You can't come back. Not even for a visit,' says Boyle, who has worked for two decades against LA's gang culture.

Boyle's Los Angeles, where daily slaughter is a grim reality, is a world away from the glamorous Hollywood hills, Malibu beaches and Sunset Strip - the celebrity-drenched city that David Beckham and Posh Spice will soon make their home.

Boyle's Los Angeles is where an estimated 120,000 gang members across five counties battle over turf, pride and drugs. It is a city of violence as a new race war escalates between new Hispanic gangs and older black groups, each trying to ethnically cleanse the other. Mayor Antonio Villaraigosa, who has referred to his city as 'the gang capital of America', has launched a crackdown on the new threat.

The latest front is the tiny strip of turf known as Harbor Gateway, a nest of streets between malls and office blocks. It was here, just before Christmas, that Cheryl Green, a 14-year-old fond of junk food and television, died. At school she had just written a poem beginning: 'I am black and beautiful. I wonder how I shall live in the future.' She never found out. As she stood on a corner talking with friends, two Hispanic members of the neighbourhood's notorious 204th Street gang walked up and opened fire, killing Green and wounding three others. They were targeted because they were black. Traditionally the outside view of LA gangs has been of black youths like the Bloods and the Crips and their countless subsets. It focused on the streets of Compton and South-Central and the culture of gangsta rap. But Hispanic gangs are in the ascendant, spreading across America.

They have names such as Mara Salvatrucha, La Mirada Locos and Barrio Van Nuys, and now the 204th Street gang - who made it clear that they will kill innocent girls to force black families off their turf.

Last year there were 269 gang-related killings in LA. Gang-related crime leaped 15.7 per cent last year, as most other types of crime fell. Hate crimes against black people have surged. With a rapidly growing Hispanic population, LA's gang culture is shifting. It means that being black in the wrong neighbourhood can get you killed.

Green's murder was the latest in a line of killings by the 204th Street gang. In 1997, 11-year-old Marquis Wilbert was killed on his bike. In 2001, Robert Hightower, 19, was killed. In 2003, Eric Butler, 39, was shot dead trying to protect his daughter from being harassed. There are streets that blacks have been forbidden to cross.

Green's death brought the gang war between 'brown and black' to public awareness. Next week a summit will be held called the Black and Brown Strategy Meeting which aims to head off a race war. 'All of the signs are there that a racial war is going to explode in this city,' says Khalid Shah, director of Stop the Violence, one of the groups organising the meeting. Memories of the 1992 Rodney King riots, which claimed 53 lives, remain fresh, but Shah believes that worse is ahead. 'It will be 10 times bigger than what happened after King. You are looking at an event which could not only paralyse an entire city but an entire state,' he warns.

Green's death sparked Villaraigosa's crackdown. The police took the unprecedented step of publishing a list of the 11 worst gangs, including 204th Street. They vowed to go after them with police, FBI agents and injunctions to prevent members meeting. An extra 50 police were assigned to anti-gang duties in San Fernando Valley. In south LA, a team of 120 detectives and 10 FBI agents has been set up. An extra 18 officers have been put into Harbor Gateway. But Angelenos have seen it all before. The city's history is littered with anti-gang initiatives, and what the new effort shows is just how widespread the gangs have become. They have spread into the San Fernando Valley, an area previously famed for suburban prosperity. Last year one area of the north Valley saw a 160 per cent rise in gang crime.

Publishing the 'hit list' could backfire. In the warped gang sub-culture, being on the list is a badge of pride. The lesson of the 204th Street gang seems apt. They number only a few dozen members in a tiny strip of city that was open fields half a century ago, but killing blacks has propelled them from obscurity to enviable notoriety.

'Putting out a list was a bad idea. Groups that don't make the list will want to be on it. They don't exactly think rationally,' said Alex Alonso, a gang historian who has testified in more than 100 court cases.

Yet there is hope. Alfonso 'Chino' Visuet, 23, was sucked into the gang life as a teenager. There was the lure of excitement and riches, the push of a difficult home life. 'People who join a gang are always running away from something. They flee to the gang,' Visuet says.

Visuet is not running any more. He works for Father Boyle's Homeboy Industries (homeboy-industries.org), a project that helps people leave gang life. It provides jobs, an education, pays to have gang tattoos removed and gives counselling. It aims to remove the circumstances that lead to crime: poverty, abuse and unemployment. It is staffed almost entirely by former gang members and has spun off a bakery, a silk-screen printers and a restaurant. 'You have to address the lethal absence of hope. I have never seen a hopeful person join a gang,' Boyle says.

It worked for Visuet. He starts college this autumn and wants to be a probation officer. 'I was on the edge of doing something that would ruin my life, either by doing violence or having it done to me. That's over now,' he says.

For the moment it is organisations like Homeboy Industries that pick up the slack. Father Boyle has a catchphrase: 'Nothing stops a bullet like a job.' But that can be a hard message to get across in a city whose political classes see gangs as primarily a police issue. That is not the way it is on the street.

Visuet despairs at the conflict. 'A brown gang member now just sees a black gang member. What they don't see is how that person comes from the same place they do. They might have a mother who is an alcoholic as well or a father who beats on them. They have the same story,' he says.

Boyle and others have mixed feelings about the crackdown. The road to LA's problems is littered with failed plans and policing, and incompetence. Over the past decade the main anti-gang scheme, LA Bridges, has spent more than $100m yet keeps no record of whether those it helps leave gang life or return to it.

Then there is political scheming. The list of 11 gangs, critics say, was drawn up deliberately to present a 'balance' by covering the whole city. Politicians use the presence of a high-profile gang to act tough on law and order and police chiefs use it as a way of upping manpower. 'It is a ridiculous list,' says Alonso.

LA is a city of two worlds - Hollywood and gangs. On a two-lane highway that roars through the middle of Harbor Gateway, a few hundred yards from where Cheryl Green was gunned down, there is a billboard for a new TV show called Sons of Hollywood. It shows three rich young men against a backdrop of palm trees. It claims to be a 'reality' show, but for most of the impoverished, racially torn citizens it is nothing more than a fantasy.