The infantrymen came under attack by a New Peoples Army (NPA) guerrilla band in the village of Illuru, near the town of Rizal early Sunday, Lieutenant Colonel Daniel Lucero told reporters.
Two air force helicopters were sent to help the beleaguered military unit, but failed to prevent the deaths.
Four soldiers and a member of the government militia forces were killed and two other soldiers were wounded, Lucero said.
The attack was launched ahead of scheduled peace talks in Norway next week with guerrilla leaders, aimed at a political settlement to the 35-year Maoist insurgency that has claimed thousands of lives.
Meanwhile, six communist rebels were killed and at least one soldier was wounded in a gunbattle in a remote town in Davao del Sur.
The military said the firefight broke out when troops from the 25th Infantry Battalion, under Lt. Col. Hernando Iriberri, clashed with more or less 50 guerrillas from the New Peoples Army (NPA) in Sitio Bantong, Barangay Donganpekong, Natanao town yesterday. With Roel Pareño