Hundreds of Filipino troops searched for communist guerrillas who killed 11 soldiers in a setback for the military's drive to defeat a four-decade insurgency before President Gloria Macapagal Arroyo leaves office in June. Seven other soldiers were wounded in the attack Saturday by about 60 guerrillas of the New People's Army near Mansalay township in Mindoro Oriental province, about 150 miles (240 kilometers) south of Manila. Several rebels may have been injured during the three-hour gunbattle, military officials said. It was the army's biggest loss in a single clash so far this year. Last month, rebels killed five soldiers and wounded eight others in a battle in the northern Philippines. “We'll be conducting an investigation if there was possible tactical blunder in the operation,” army Lt. Gen. Roland Detabali said. “It might have not been well-supervised.” Detabali wondered why the soldiers, who had been searching for a group of rebels, ventured out at daybreak when they could be easily seen, instead of launching an offensive at night. Air force helicopters brought the remains of the dead to Manila on Sunday. About 1,000 soldiers, including reinforcements from nearby Quezon province, have been deployed to hunt down the guerrillas, Detabali said. In separate fighting Sunday, an army lieutenant and five communist rebels were killed in a clash in a village near central Cadiz city that broke out when an army patrol stumbled on a group of rebels, army spokesman Lt. Col. Arnulfo Marcelo Burgos said. Arroyo has ordered the military to end the communist rebellion, one of Asia's longest, by the end of her term in June. The rebels have dismissed the deadline. The rebels say they are fighting to set up a Marxist state in the country. Their ranks have thinned to about 4,000 from a peak of more than 25,000 in the mid-1980s because of battle setbacks, surrenders and factionalism. Peace talks between the rebels and the government brokered by Norway collapsed in 2004 after the rebels accused the Philippine government of instigating their inclusion on US and European terrorist blacklists.