MORELIA, Mexico (AP) -- Gunmen killed a police chief and two officers Thursday in the same western town where a human head was dumped a day earlier.
Antonio Bravo, police chief of Quiroga, and two officers were attacked while they drove in a patrol car, Michoacan state prosecutors said in a statement.
Quiroga authorities found the severed head Wednesday in the town's tree-lined plaza near city hall. It was accompanied by a threatening message referring to a drug cartel.
Also Thursday, police in the Michoacan town of Zitacuaro found several plastic bags containing body parts near the city government offices, prosecutors said.
And in the Pacific Coast state of Sinaloa, a man was hanged from a bridge in the Villa Union, about 12 miles (20 kilometers) from the resort city of Mazatlan.
Police found a message threatening the Zetas, a gang founded by former-soldiers-turned-hit men who also work with the Gulf cartel, state Attorney General's Office spokesman Martin Gastelum said.
Gastelum said the unidentified man had been tortured first.
Sinaloa is Mexico's drug-smuggling heartland and the birthplace of the leadership of four of the six major cartels.
Drug violence has killed more than 15,000 people nationwide since President Felipe Calderon launched a crackdown on cartels in late 2006.