At least six gunmen died in separate shootouts with federal law enforcement agents and army troops in Piedras Negras, a border city in the northern Mexican state of Coahuila, officials said.

The first shootout occurred around 10:30 a.m. on Monday and involved federal law enforcement agents and gunmen, with four suspected criminals ending up dead, Coahuila Attorney General's Office spokesmen told Efe.

Two federal law enforcement agents wounded in the shootout were taken to a hospital in the border city.

The second shootout occurred just after 3:00 p.m. in the southern section of Piedras Negras, officials said.

Army troops and Federal Police officers engaged a group of gunmen, killing two of them.

A vehicle and two rifles were seized after the shootout.

The Federal Police and the army launched a series of operations across the border city on Monday morning, security spokesman Sergio Sisbeles said.

The prison in Piedras Negras was the scene of a massive jailbreak on Sept. 17.

A total of 131 inmates escaped from the prison in an incident blamed on the Los Zetas drug cartel.

Heriberto Lazcano Lazcano, the top Los Zetas boss, was killed in a shootout with marines in Coahuila state on Oct. 7.

Lazcano, known as "El Lazca," deserted from the Mexican army in 1999 and formed Los Zetas with three other soldiers, all members of an elite special operations unit, becoming the armed wing of the Gulf drug cartel.

After several years on the payroll of the Gulf cartel, Los Zetas, considered Mexico's most violent criminal organization, went into the drug business on their own account and now control several lucrative territories. EFE