MANILA, Philippines - A body found Wednesday in a rice field in Shariff Aguak, Maguindanao province has been identified as a teenager who was allegedly a member of the Civilian Volunteer Organization (CVO) or private army of the Ampatuans.

The body of 16-year-old Jamidin Galumpa, a farmer and resident of Mamasapano town, was identified by his parents, said Lt. Col. Michael Samson, spokesman of the Armed Forces' Eastern Mindanao Command.

He is the first casualty after President Gloria Macapagal Arroyo imposed and lifted martial law in Maguindanao following the November 23 massacre of 57 innocent civilians in the country's worst election-related killings.

Authorities believe Galumpa was with a group of armed men who fired at security forces who were unearthing an arms cache near the mansion of former Maguindanao governor Andal Ampatuan Sr. last Monday.

The Shariff Aguak police said Marian Galumpa, the boy's mother, reported that her son was missing last December 12. She said she did not know how the boy ended up in the company of armed men, police added.

Samson said the boy was part of a Civilian Volunteer Organization (CVO) loyal to the Ampatuans, who were encountered by security forces at the back of Ampatuan Sr.'s mansion in Sitio Bagong, Barangay Timbagan on Monday night.

He said the security forces were unearthing firearms at the back of the former governor's mansion when they were fired at by the armed group. The security forces fired back, possibly killing the boy, the spokesman said.

Police said the boy could have been hurriedly buried by the armed group in the rice field and then escaped.

The discovery of the suspected CVO member's identity comes after a self-confessed killer revealed to ABS-CBN News that he was a child assassin who killed more than 100 people for the Ampatuan clan. (Read article: Ex-child assassin: 'I killed hundreds for the Ampatuans')

President Gloria Macapagal Arroyo on Saturday lifted Proclamation 1959, which imposed martial law and suspended the writ of habeas corpus in Maguindanao beginning November 28.

The government said martial law was declared in the province to prevent a looming rebellion led by members of the Ampatuan clan.

Authorities claim that several groups of armed men were seen massing and gearing for an armed rebellion against the government to prevent the arrest of Ampatuan clan members allegedly involved in last month's massacre in Ampatuan town. With a report from from Jun Lingcoran, radio dzMM