CIUDAD JUAREZ, MEXICO - A US Air Force sergeant was among six people shot dead by masked men in a strip bar in Mexico's notoriously violent border city of Ciudad Juarez, local and US officials said Wednesday.

Three other US service members were also wounded in the attack, according to an official from the state deputy attorney general's office who declined to be named.

A military spokesman confirmed the death of Air Force staff sergeant David Booher in the incident and said Mexican police were investigating.

Booher was attached to the 49th medical group at Holloman Air Force base in New Mexico, base spokesman Tom Fuller told AFP.

A second US service member was seriously injured, and two others were slightly hurt, the local justice official said, adding that all three would be treated in El Paso.

The US Consulate in Ciudad Juarez declined to comment on the deaths.

Police said earlier that attackers had tried to remove six unidentified men from the bar before shooting them dead, and that three others had been injured.

More than 60 people were in the bar at the time of the attack, according to witnesses.

Thirteen others died in various attacks overnight in the same state of Chihuahua, which is at the heart of a wave of suspected drug-related violence which has left some 14,000 dead since the end of 2006.

Five of the deaths were in Ciudad Juarez, where more than 2,000 people have been killed this year despite the deployment of 8,500 troops.

President Felipe Calderon deployed some 50,000 security forces across the country after he took office in December 2006, in a controversial crackdown on powerful drug cartels.