Five federal police and a suspected hitman were killed in a shootout Tuesday as authorities surrounded a house in Culiacan, home to the Sinaloa drug cartel.
Four other federal police were hospitalized with wounds, and police took several suspected cartel members into custody, according to a federal police official who wasn't authorized to give his name.
Mexican President Felipe Calderon sent nearly 3,000 federal police and soldiers into Sinaloa state two weeks ago as part of his campaign to take back parts of Mexico controlled by drug lords. In all, Calderon has sent more than 20,000 security forces to confront the drug trade, and the cartels have responded by targeting police and other security officials.
At least three banners threatening 21 local police officers by name were hung in the violent northern city of Chihuahua over the weekend.
"The officers are uneasy," Chihuahua state prosecutor's spokesman Eduardo Esparza said Tuesday. "They have been instructed to be in direct contact with the police station and to be extremely careful."
In the nearby border city of Juarez, a death list of 22 officers was left at a monument to fallen police four months ago, addressed to "those who still don't believe" in the power of the cartels.
Of the 22, seven have been killed and three wounded in assassination attempts. All but one of the others have quit.