All of the dead were believed to be drug traffickers, possibly rival members of the same drug cartel, Baja California state Attorney General Rommel Moreno said.

He refused to specify the cartel. The Tijuana-based Arellano Felix gang has been shaken by the arrests or deaths of many of its key leaders.

Police did not identify any of the dead or wounded.

In one of the shootouts, gunmen exchanged fire between sport utility vehicles speeding down a six-lane boulevard in Tijuana.

The first shootout claimed seven victims. Three subsequent gunbattles -- one outside a hospital -- claimed five more. Police said the body of the 13th victim turned up at a city hospital, and local news media reported the deaths of two others who were hospitalized.

The attorney general's office said eight suspects were being treated at the heavily guarded hospital, and local newspapers said it canceled outpatient services and laboratory work. Hospital officials could not be reached for comment.

In 2007, gunmen opened fire on state police guarding the same hospital, where gang members were being treated for gunshot wounds.

The suspects are being held on suspicion of weapons possession among other possible charges.