Gunmen stormed two homes and massacred 13 young partygoers in the latest large-scale attack in this violent border city, even as a new government strategy seeks to restore order with social programs and massive police deployments.

Attackers in two vehicles pulled up to the houses in a lower-middle-class neighborhood late Friday and opened fire on about three dozen youths attending a party. The dead identified so far were 16 to 25 years old, the Chihuahua state attorney general's office said Saturday in a statement. Fifteen were wounded, including a 9-year-old boy.

Police found 70 bullet casings from assault weapons typically used by drug gangs whose bloody turf battles have killed more than 2,000 people this year in Ciudad Juarez, across the border from El Paso, Texas.

The attackers escaped, and police said they had no immediate information on any suspects or possible motive.

Ciudad Juarez has become one of the world's deadliest cities amid a turf war between the Sinaloa and Juarez cartels, which frequently go after each other in mass attacks on bars, drug rehab centers and parties.

Some have resulted in apparently innocent people being killed, either because someone else at a gathering was the target or gunmen simply had the wrong address.

Most recently, attackers stormed two homes on Oct. 17, killing seven at a party and two more in another house nearby.

And in January, gunmen massacred 15 people at a party in a house not far from the site of Friday's killings. Most of the victims were teenagers, students and athletes.

Investigators later said the attack was apparently carried out by Juarez cartel gunmen looking to kill allies of the Sinaloa cartel. There is no evidence the youths were the targets, and police said the killers may have hit the wrong house.

The city was outraged by the January massacre, leading President Felipe Calderon's government to vow to implement a new strategy for restoring order in Ciudad Juarez, where the army had by then had replaced the disorganized, outgunned local police.

In April, federal police took over public security duties from the army, and about 5,000 federal officers were deployed in Ciudad Juarez.

The federal government also stepped up social programs to try to break the cycle of poverty, broken homes and lack of opportunities that make the city's youths a fertile recruiting ground for the gangs.

Cash aid programs, neighborhood improvement initiatives, educational and job-training programs were part of the new strategy, together with ubiquitous convoys of blue federal police trucks patrolling "safe corridors" throughout the city.

But in light of the recent mass attacks, it is unclear whether the new strategy for the city is having an effect so far. While the bustling industrial hub was known mainly throughout the 1990s for the grisly series of murders of more than 100 young women, the city's youths now bear the brunt of the violence.

In an interview with The Associated Press earlier this month, President Felipe Calderon said the Juarez strategy is a long-term policy.

"We cannot think that all the ground lost regarding opportunities for these young people can be recovered in a few weeks," Calderon said. "If we are building five new high schools and two universities, don't tell me it's not working if classes started a month ago."