Gunmen have killed eight people in a bar in the northern Mexico city of Monterrey, the scene of recent bloody turf battles between the Gulf drug cartel and the Zetas gang.

Nuevo Leon state security spokesman Jorge Domene said a ninth person died when he apparently fell trying to flee the attackers across rooftops. The attack happened on Monday evening at the Matehuala Men's Club.

Domene said some of the victims were bar employees. Authorities are investigating motives behind the attack, but say a recent upsurge in violence is a result of fighting between the Zetas and the Gulf cartels.

In the city of Reynosa, across the border from McAllen, Texas, the Mexican army reported clashes that left four gunmen dead.

The army said armed men attacked a patrol in the town centre of Reynosa, leaving four people dead. Presumed allies of the gunmen set up roadblocks throughout the city in order to stop army units moving freely.

The military did not release the identities of any of the dead.