Guadalajara - Gang gunmen opened fire on a Jalisco state security convoy in western Mexico on Monday, killing an undetermined number of people in the latest clash to hit the region.
An official in the state prosecutor's office, who asked to remain anonymous, told AFP that there were several fatalities.
The official did not provide more details, but local media said at least 15 people were killed.
The Milenio media group said all the fatalities were members of the Jalisco Unified Force, a unit of the state prosecutor's office.
In a statement, the Jalisco prosecutor's office said "several of our officers were hit by bullets", but it did not indicate how badly they were hurt or how many were struck.
Investigation
The attack took place on a highway near the village of Soyatan as the Jalisco Unified Force headed to Guadalajara, Mexico's second biggest city, the statement said.
The statement said the ambush appeared to be in revenge over the arrest of gang suspects in an investigation into the attempted murder of Jalisco's security chief on 30 March.
Fifteen suspects are under investigation over the attack against security commissioner Alejandro Solorio Arechiga. Four of them have been detained.
The attack against Solorio was itself a response to a 23 March operation in the town of Zacoalco de Torres in which three gang suspects were killed, the statement said.
The authorities did not identify the gang but the state is known as a bastion of the Jalisco New Generation drug cartel.
A gang launched a deadly ambush against federal police in the town of Ocotlan on 19 March, leaving 11 people dead, including five officers, three suspects and three bystanders.
The Jalisco prosecutor's office said more details about Monday's attack would be made public in the coming hours.