MEXICO CITY (AP) — The Mexican government sent 300 National Guard troopers to bolster the southern state of Guerrero on Tuesday, where a local police chief and 12 officers were shot dead in a brutal ambush the day before.

It was just one of three attacks Monday in an increasingly violent region of the country.

Announcing the reinforcements in his morning news conference, President Andrés Manuel López Obrador mourned the victims and called the attack “practically an ambush.”

Guerrero's attorney general launched an investigation Monday after the 13 bodies were found on a highway in El Papayo, which is in the Guerrero township of Coyuca de Benítez on the Pacific coast. Two more people were injured in the attack.

Some bodies were found handcuffed, face down on the ground, according to local reports, which could suggest the attackers ambushed and captured the police officers before killing them.

Authorities did not provide any more details about the attack or those responsible.

At least six more people were killed Monday in two other attacks in Mexico's southwest, a region where escalating gang conflicts are pushing a surge of violence.

Earlier this year, two police officers and three civilians were killed in an attack attributed to the Familia Michoacana cartel. Then in August, a leader of the rival Arreola gang was assassinated. Since then people in the region have complained increasingly about little official security against gangs.

According to figures from Common Cause, 341 police officers have been killed in Mexico so far this year. In 2022, at least 403 were slain.