Massive gunbattles broke out between suspected drug traffickers who fired at each other while speeding down heavily populated streets of this violent border city early Saturday, killing 13 people and wounding nine.

All of the dead were believed to be drug traffickers, possibly rival members of the same cartel who were trying to settle scores, said Rommel Moreno, the attorney general of Baja California state, where Tijuana is located.

"Evidently this is a confrontation between gangs," Moreno told reporters.

Eight suspects and one federal police officer were injured in the pre-dawn shootings, none gravely, said Agustin Perez Aguilar, a spokesman for the state public safety department. The suspects are being held on suspicion of weapons possession among other possible charges.

Police recovered 21 vehicles, many with bullet holes or U.S. license plates; a total of 54 guns; and more than 1,500 spent shell casings at various points in the city where the battles broke out, Perez Aguilar said.

At one point, the alleged traffickers fired at one another as their sport utility vehicles sped down a busy six-lane boulevard lined with restaurants, car repair shops, medical offices and strip malls.

Bullet holes could be seen in the walls of a factory building and on the perimeter wall of a housing complex along the road, but no bystander deaths were reported. It was not clear how long the gunbattles lasted.

A mall security guard who did not want to give his name for fear of reprisals said he heard hundreds of gunshots fired, some of which passed near him.

"I hit the ground," the guard said. When he got up again, he said he saw bullet holes in the wall behind him, a dead man lying in a pool of blood and 11 abandoned, bullet-ridden SUVs on the street.

The first shootout claimed seven victims. Three subsequent gunbattles — one outside a hospital — claimed five more, police said. The body of a man police believe to be the 13th victim turned up at a city hospital.

Tijuana, a sprawling metropolis just across the border from San Diego, California, is pervaded by frequent violence, much of it blamed on drug cartels battling for control of lucrative trafficking routes. The city is home to the Arellano-Felix drug cartel.

In January, eight people died in a gunbattle at a Tijuana safe-house apparently used by drug hit men to hold kidnapped rivals. In that confrontation, hit men holed up inside the house battled police and soldiers with automatic weapons for three hours.