Mexico City, Oct 24 : At least 13 police officers were killed in an armed attack in Mexico's Guerrero state, authorities said. The state attorney general's office said theincident occurred on Monday in the town of El Papayo under the municipality of Coyuca de Benitez, reports Xinhua news agency. The policemen were attacked by a group of armed men near the Acapulco-Zihuatanejo federal highway, according to police reports. Gabriel Alejandro Hernandez Mendoza, Guerrero's deputy prosecutor of investigations, confirmed that among the dead are two police chiefs, one of whom is the secretary of public security of Coyuca de Benitez, Alfredo Alonso Lopez. The National Police havedecided to strengthen its presence and surveillance in the city of Coyuca de Benitez. Guerrero is one of the Mexican states most affected by the violence of criminal groups, which in recent months have intensified their attacks against security agencies combatting them. /IANS