Three people were killed and two others wounded by gunfire -- including a 3-year-old -- Thursday in Tijuana.
The girl was wounded in the chest by a drive-by shooter Wednesday. A 22-year-old woman with her was killed.
The news came as part of wave on drug violence again swept northern Mexico. In the beach town of Rosarito, a deputy police commander was gunned down early Thursday while on patrol, the Baja California state prosecutor's office said.
Eight officers have been killed this year in Rosarito, a beach city about an hour's drive south of San Diego.
Near the Baja California border city of Tecate, two beheaded bodies wrapped in duct tape were found along a highway on top of an overturned bucket.
Elsewhere, a shootout between rival gangs killed 10 people in the drug-plagued state of Sinaloa, home of the powerful cartel of the same name, Mexican police said Thursday.
The gun battle occurred in front of a state police station in the town of El Rosario, said Juan de Dios Beltran, an agent with Mexico's federal attorney general's office. Two vehicles, nine assault rifles, several handguns and about 200 shells were found in the area after the shootout late Wednesday, he said. There were no arrests.
The state prosecutor's office said in a news release that gunmen later shot up the outside of a Mazatlan clinic where a man believed wounded in the shootout was treated. Police were searching for the man, who left after his surgery.
Baja California and Sinaloa are among the top states for drug-related killings, according to the attorney general's office. Organized-crime slayings have more than doubled this year as powerful drug cartels fight each other for control.
Attorney General Eduardo Medina Mora has said more than 5,300 people have died in gangland style killings in 2008.