Graffiti artist George Curiel, 38, looks at his mural artwork last month in central Los Angeles. Once armed only with cans of spray paint, graffiti crews have taken up arms in recent years to protect their work.

Los Angeles ? One man got stabbed. Another got shot in the chest. A 6-year-old boy was temporarily blinded when he was spray-painted in the face.

And they were the lucky ones among those who have had run-ins with graffiti “crews,” or gangs.

Over the past 2 1/2 years in Southern California, three people have been killed after trying to stop graffiti vandals in the act. A fourth died after being shot while watching a confrontation between crews in a park.

“We have seen a marked increase in these graffiti-tagging gangs taking to weapons and fighting to protect their walls, their territory, their name,” said Los Angeles County sheriff’s Lt. Robert Rifkin.

Los Angeles County has battled graffiti for decades, spending $30 million a year to paint over or clean up the emblems, names and other images spray-painted on stores, concrete-lined riverbeds, rail lines, phone booths, buses, even police cars. On Wednesday, Gov. Arnold Schwarzenegger signed a law requiring convicted graffiti vandals to remove their scrawl.

For some taggers, protecting their work is akin to defending their names and their honor.

“If we see someone calling the police, then we target them,” said Mario Garcia, 20, who describes himself as a former tagger trying to become a professional artist. “You are trying to stop me from what I live, what I believe in and what I breathe? We are not going to let no one get in the way.”

Workers who remove the graffiti say they take caution if they find a crew at work. They wait until the taggers leave before cleaning up.

“We won’t say anything to them,” said Rogelio Flores, whose company Graffiti Busters contracts with Los Angeles to blast away the markings with high-pressure hoses. “We don’t know what kind of weapons they have.”

Police tell residents to resist the urge to confront graffiti crews.

“It’s not worth the risk,” Rifkin said. “Take a deep breath, back off and call law enforcement.”

Some of the violence has been between rival crews, which are increasingly acting like street gangs. And some of the bloodshed has involved real street gangs that mark their turf with their names or emblems. But some of the victims have been innocents.

In an attack last month, two youths spray-painted the face and body of the 6-year-old boy who spotted them scribbling gang signs on a wall near Compton. The boy recovered from chemical burns to his eyes.