At least 37 people were killed over three days in the Mexican border city of Tijuana, including four children caught in shootouts and nine men found decapitated, the state attorney general said Monday.
More than 200 people have been killed in the past month in Tijuana, where officials say rival cells of the Arellano-Felix drug cartel have been waging a bloody battle across the border from San Diego.
Tijuana's police chief was fired Monday after the wave of violence. A statement from the office of Tijuana Mayor Jorge Ramos says Alberto Capella was replaced by his second-in-command, army Cmdr. Julian Leyzaola.
No reason was given for Capella's abrupt dismissal.
Baja California state Attorney General Rommel Moreno said three police officers were among the nine decapitated men, whose bodies and heads were discovered in a poor Tijuana neighborhood. Their police credentials were found stuffed in their mouths.
Police were investigating whether some of the 37 deaths between Saturday and Monday were part of a retaliatory spree sparked by the killing of a 25-year-old woman believed to be a drug trafficker's girlfriend, Moreno said.
He said interviews with families members indicated that 80 percent of the victims had been involved in drug dealing.
But four of the dead were children.
Two brothers, aged 4 and 13, had been waiting for their parents outside a convenience store when gunmen opened fire, killing the boys and several adults. A 14-year-old boy working at locksmith's kiosk was shot dead in an attack on a neighboring business. And a 12-year-old was killed when the car he was riding was sprayed with bullets.
Violence is soaring
Violence has soared in Mexico as drug cartels compete for smuggling routes and battle government forces.
In the northwestern state of Sonora, a 15-year-old boy was found shot to death under a tree. Police named no suspects or motive.
In southern Michoacan state, gunmen burst into the offices of a local cattle ranchers' association and killed one of its directors, a 27-year-old woman. Police arrested two suspects but gave no possible motive.
Mexican newspapers have reported that more than 4,000 people have been killed across the country this year in drug-related violence.
The federal government does not regularly release homicide figures, although officials have acknowledged that killings have surged in the last two years.
Since taking office in 2006, President Felipe Calderon has sent more than 20,000 soldiers across the country to root out cartels, a crackdown that is popular among many Mexicans.
A poll published Monday by the daily Reforma says 64 percent approve of the job Calderon is doing. The poll interviewed 1,515 adults and had a margin of error of 2.5 percentage points.