A five-year-old child was killed and six others wounded after a bomb ripped through a public bus on a highway near Cotabato City on Mindanao island.

The wounded included a five-month-old baby and a three-year-old child.
The wounded included a five-month-old baby and a three-year-old child. (AFP)

A child has been killed and six others wounded after a bomb exploded on a public bus in the insurgency-plagued southern Philippines, authorities have said, but no group has claimed responsibility.

Police on Tuesday said the explosion happened as the bus was travelling along a highway near Cotabato City on Mindanao island, a haven for multiple armed groups ranging from communist insurgents to extremist militants.

The bomb was "inside the bus, at the end part ... where there were a lot of people sitting," said Chief Master Sergeant Randy Hampac, police spokesperson in Aleosan town.

A five-year-old boy died, while six others were wounded in the blast that shattered the back windows, Hampac said.

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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.

'It's the first time'

"It was the first time for this to happen in our town," Hampac said.

"There were incidents of bombing of cell towers in previous years but this incident of an explosion in a bus, it's the first time."

Regional military spokesman Lieutenant Colonel John Baldomar said no group had admitted carrying out the "presumed attack".

Militant attacks on buses, Catholic churches and public markets have been a feature of decades-long unrest in the region.

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In May 2017, hundreds of pro-Daesh 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 claimed more than a thousand lives.

Source: TRTWorld and agencies