Police say the blast took place as the bus travelled near Cotabato City on Mindanao island, where armed groups are active.
A child has been killed and six others wounded after a bomb exploded on a public bus in the rebellion-plagued southern Philippines.
Police said the explosion took place on Tuesday as the bus was travelling along a highway near Cotabato City on Mindanao island, a haven for multiple armed groups ranging from communist rebels to religious fighters.
The bomb was “inside the bus, at the end part … where there were a lot of people sitting”, according to Randy Hampac, police spokesman in Aleosan town.
A five-year-old boy died in the blast that shattered the back windows, Hampac said. The wounded included a five-month-old baby and a three-year-old child.
A police report said one of the victims saw a male passenger leave “baggage” on the bus when he disembarked and it later exploded.
Regional military spokesman Lieutenant Colonel John Baldomar said no group had admitted carrying out the “presumed attack”.
Attacks on buses, Catholic churches and public markets have been a feature of decades-long unrest in the region.
Manila signed a peace pact with the nation’s largest rebel group, the Moro Islamic Liberation Front, in 2014, ending their deadly armed rebellion.
But smaller bands of fighters opposed to the peace deal remain, including fighters professing allegiance to the ISIL (ISIS) group. Communist rebels also operate in the region.
In May 2017, hundreds of pro-ISIL foreign and local gunmen seized Marawi, the country’s largest Muslim city.
The Philippine military wrested back the ruined city after a five-month battle that killed more than 1,000 people.