Gunmen armed with AK-47s opened fire on a state police patrol in the first incident, which happened Tuesday evening outside the small town of El Coacoyul, near the Pacific coast resort of Zihuatanejo, the state government said.

“The officers returned fire and repelled the attack, in an exchange that lasted about 30 minutes. Ten suspected criminals were killed,” state security spokesman Roberto Álvarez said in a statement.

One police officer was also wounded in the shootout. Álvarez said the army and marines were sent in as reinforcements.

Shortly after the first attack began, gunmen ambushed another state police patrol on a highway in the nearby town of Las Mesillas, killing six officers.

Alvarez said the second ambush may have been in retaliation for the first shootout.

Guerrero, the scene of drug cartel turf wars, registered 2,318 murders in 2017, making it the most violent state in a year that set a record for violence in Mexico, with more than 25,000 homicides nationwide.

Across Mexico, more than 200,000 people have been killed since 2006, when the government deployed the army to fight drug trafficking.