Upheaval in Central America is renewing itself in the barrios of Los Angeles, where the influx of refugees into some of the city's most troubled neighborhoods has led to the rise of a new generation of youth gangs, authorities say.

Gangs of young men with roots in El Salvador, Guatemala and other Central American nations make up about 5% of the city's estimated 300 youth gangs, Los Angeles police say. But the influence of these Central American gangs is growing as they carve out niches in the San Fernando Valley and in the inner city, according to police and other gang experts.

Mara Salvatrucha, a Salvadoran gang that came into existence only six years ago, has grown to 500 members, making it as large as entrenched Mexican-American gangs, authorities say. Members of Mara Salvatrucha and Crazy Riders, another gang with largely Central American membership, have been linked by police--either as victims or suspects--to five murders. Authorities say, however, they suspect that the gangs are involved in many other killings.

"They're on the increase, and they're making a name for themselves," Detective Robert Contreras, of the Los Angeles Police Department's Gang Information Section, said of the city's Central American gangs.

The proliferation of Central American gangs is especially troubling because members have a greater tendency to react with violence, police say. Authorities attribute this to the horrors that many Central Americans have witnessed back home, such as seeing family members executed by Salvadoran death squads.

"In their countries, they're used to bombs and decapitated bodies," said Manuel Velasquez, a spokesman for the city's Community Youth Gang Services agency in the San Fernando Valley. "They laugh at drive-by shootings."

Police arrested two alleged members of the Crazy Riders on Nov. 10 in connection with the drive-by shooting in Van Nuys of Walter Adama, 17, killed while standing in front of his home on Fulton Avenue. Police also suspect these gangs of involvement in a rash of car thefts several months ago in the area.

The Crazy Riders also was implicated in a major turf battle late last month with another Latino gang near MacArthur Park, in which two people were killed and six were injured.

"We're very concerned because they don't hesitate to exert influence on other gangs," said Detective Cliff Ruff of the Police Department's Foothill Division in the Valley.