An 11-year-old girl was killed and at least 32 people were injured after a crude bomb kept beneath a seat in a bus exploded on Friday in a southern Philippine city.

Zamboanga City Mayor Beng Climaco told local media that the blast took place around 2.15 pm near a crowded marketplace, where the bus was loading  passengers. In a press brief the local police informed: "At about 2:15 p.m. 18 September, 2015 an explosion occurred inside a Biel Bus parked at Morga Compound located along Calixto St, Zamboanga City."

As many as 32 people were reported injured. According to Manila Bulletin, the youngest passenger injured in the bus bomb blast is one-year-old, while the oldest is 75-year-old.

Images shared on social media show that it was a "powerful explosion". Local TV channel TV 11 noted: "This is terrible... the explosion is so powerful that it wrecked the bus."

Another report, citing a local journalist at the scene, noted that the blast ripped the bus.

The police suspect that the bomb was planted by terrorists from banned Islamist group Abu Sayyaf, ABC news reported. 

Abu Sayyaf, which is declared a terrorist group by the Philippines and is also on Washington terror list, had previously bombed civilian targets in Zamboanga City.

The radical Islamist group that started off as an organisation demanding a separate Muslim state is now notorious for beheading hostages, ransom kidnappings of Filipinos and foreigners.