Unidentified gunmen ambushed a convoy of five police vehicles in the western Mexico state of Jalisco on Thursday, killing nine officers and leaving one missing.
The 20 officers in the convoy were outnumbered by the attackers, who were riding in about ten 4x4 vehicles, the Jalisco state public safety department said.
The ten officers who survived the attack fought an hours-long battle with the gunmen, and several were wounded.
The attackers used grenades and assault rifles before fleeing into neighbouring Michoacan state.
Michoacan is home to the violent La Familia cartel, which has been known to launch fierce attacks on police convoys.
Jalisco authorities complained that Michoacan officials had not joined in the search for the attackers.
Meanwhile in Zapopan, a suburb of the Jalisco state capital of Guadalajara, two two-year-old boys and three other people were wounded by grenade fragments during an attack on a private home.
The Zapopan municipal police department said the toddlers, a 17-year-old girl and two adults were all were bystanders on a street outside the home, and said none of the wounds appeared life threatening.
Witnesses said men in a pick-up fled after two explosions were heard. The attack appeared directed at a house located close the local church.
Also on Thursday, the United States delivered three mobile X-ray inspection vehicles to Mexico as part of the Merida Initiative anti-drug aid plan. Mexico's tax agency said the vehicles will be used to inspect freight and merchandise shipments to detect irregularities.