At least 11 people were killed and 21 wounded when a bomb exploded inside a passenger bus in the southern Philippine province of Bukidnon on Tuesday evening.
Major Christian Uy, spokesman of the Army's 4th Infantry Division, said a Rural Transit bus was traveling near the Central Mindanao University campus in Maramag town when the bomb exploded at about 5:45pm.
Many of the victims were high school students who had just boarded the bus as it passed a school in the town, said Lieutenant Norman Tagros, spokesman for a local infantry brigade.
The bomb went off almost immediately after the students got on.
Tagros said extortion was being eyed as the likely motive. The bombing was the latest in a series of attacks on the bus company.
The bus was coming from Wao town in Lanao del Sur en route to Cagayan de Oro City at the time of the explosion.
Uy said the injured passengers were taken to a hospital in Valencia town.
Last month a bomb exploded aboard a Rural Transit bus in Mindanao, leaving four people injured.
Ten people were killed when a bomb exploded aboard a bus operated by the same company on Mindanao in 2010, which was blamed on an extortion scheme linked to Muslim extremists.
Additional reporting by AFP.