Gunmen stormed a bar and shot dead six people in Mexico's notorious northern border city of Ciudad Juarez, police said Wednesday.

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

A group of masked men armed with assault rifles entered the Ciudad Juarez bar and tried to remove six men before shooting them dead. They also injured three others seated at a table, police investigators said.

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

Two triple homicides, including three women shot dead in the mountainous Tarahumara region, were among 13 other killings in the northern state, authorities said.

Five of the deaths were in Ciudad Juarez, the country's most violent city 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 troops across the country after he took office in December 2006 in a controversial crackdown on powerful drug cartels.