Army troops captured nine suspected Los Zetas cartel gunmen in Vallecillos, a city in the northern Mexican state of Nuevo Leon, where 21 hired guns died over the weekend, the Defense Secretariat said.

The suspects were paraded before reporters Monday at the Nuevo Leon State Investigations Agency, or AEI, headquarters in Monterrey, the state capital.

The gunmen were captured on Sunday near the town of San Carlos, the secretariat said.

The suspects belonged to the Los Zetas cell led by Marco Garza de Leon, who was arrested over the weekend, the secretariat said.

A total of 21 gunmen were killed in Vallecillos over the weekend, including three on Friday, nine on Saturday and nine on Sunday.

Garza de Leon, the suspected Los Zetas boss in several cities in Nuevo Leon, and three associates were captured by army troops on Friday in Vallecillos.

Army troops, marines and Federal Police officers moved into the area after Garza de Leon's arrest to deal with Los Zetas, which had a training camp in Vallecillos, located about 100 kilometers (62 miles) north of Monterrey.

Garza de Leon was detained in a joint operation staged by the army, the Federal Police and the AEI in Vallecillo.

He was in charge of drug sales for Los Zetas in four rural cities in northern Nuevo Leon, where he also staged kidnappings, ran extortion rackets and smuggled drugs, officials said.

Nuevo Leon has been battered by a wave of drug-related violence since March 2010, when three rival cartels reportedly went to war with Los Zetas, considered Mexico's most violent criminal organization.

Los Zetas has been battling an alliance of the Gulf, Sinaloa and La Familia drug cartels, known as the Nueva Federacion, for control of the Monterrey metropolitan area and smuggling routes into the United States.

The most brutal incident in the turf war occurred on Aug. 25, when suspected Zetas gunmen set fire to Monterrey's Casino Royale, killing at least 52 gamblers and employees trapped inside, most of whom died of smoke inhalation.

Heriberto Lazcano 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.