Marine Major General Benjamin Dolorfino, a regional military commander, said the explosive left near an old municipal hall in Indanan town did not detonate properly and caused no damage.

He said the bomb was made from ammonium nitrate fitted into an 81mm mortar shell and wired to a cell phone used to trigger an explosion. Soldiers frequently pass the road where the bomb was planted.

No individual or group claimed responsibility for the blast, but previous attacks have been largely blamed to Abu Sayyaf militants, whose group is allied with the Jemaah Islamiya.

“We are still investigating who was behind this,” Dolorfino told the independent newspaper, the Mindanao Examiner.

Fighting between militants and security forces have subsided the past weeks. Fierce clashes since September left dozens of Abu Sayyaf gunmen and soldiers dead and wounded, including two US Special Forces members who were assisting the local military in defeating the militant group. -- Mindanao Examiner