Drug gangs have escalated a violent turf war in the past weeks in Guadalajara [AFP]

Armed men have opened fire and hurled a grenade into a crowded nightclub in the Mexican city of Guadalajara, killing six people and wounding at least 37.

The grenade was thrown at the porch of the bar in Mexico's second most populous city, police said on Saturday.

Three women and three men were killed in the attack and more than 20 people were wounded. The assailants fled in several cars.

This is the second grenade attack on a Guadalajara bar in less than a month: On January 16 an argument between gunmen and musicians ended in a blast that killed two people.

The latest attack took place just hours after a shootout between soldiers and presumed cartel gunmen left eight people, including an innocent driver, dead in the northeastern city of Monterrey.

Monterrey is at the intersection of several highways - often used as drug smuggling routes - heading north into the US.

Two rival drug organisations, the Gulf cartel and their former allies, the Zetas, are battling for control of the area.

The incidents in Monterrey and Guadalajara brought the overall death toll of this weekend's drug-related violence to at least 30.

In Chihuahua state, 11 people were killed in several separate murders in Ciudad Juarez, Mexico's deadliest city, across from the US city of El Paso, Texas between late Friday and Saturday, authorities said.

And gunmen shot dead five men together in an additional group killing on a highway between Chihuahua city, the state capital, and Ciudad Juarez, police said.

Separately, a special unit of soldiers and police known as the Immediate Reaction Group stopped two suspicious vehicles in a suburb of the industrial city of Monterrey, the secretariat of defence said. The car occupants responded by pulling out weapons and opening fire.

"Seven alleged aggressors lost their lives" in the shootout, the secretariat said in a statement, adding that the attackers "struck the side of a vehicle, resulting in a civilian death".

More than 34,600 people have died in drug trafficking related violence since December 2006, when the government of President Felipe Calderon deployed soldiers and federal police in a widespread crackdown on the illegal cartels.

Source: Agencies