At least nine people have been killed and 20 injured in an explosion on the southern Philippine island of Jolo, police and witnesses have said.
The blast occurred at a grocery shop on a busy street in Jolo town, local police chief Ajiron Ajirim said.
No-one has claimed responsibility for the attack but local police suspect the al Qaeda-linked militant group Abu Sayyaf of involvement.
One person is being held for questioning by authorities.
The explosive device, which detonated at about 1300 (0500GMT) was planted on the ground floor of a two-storey building in Jolo town.
Those killed were mostly employees working in the Sulu Consumers' Co-operative, Senior Superintendent Ajirim said.
Police have set up road blocks around the town and many businesses have closed.
More than 20 people with severe burns have been taken to Jolo's provincial hospital, according to an AFP reporter in the area.
In February, one civilian was killed and 20 others were seriously wounded in a bomb attack by insurgents at a bar near a Philippine Army camp in Jolo.
Abu Sayyaf is the smallest and most violent Islamic separatist group in the Philippines.
It is infamous for kidnapping Westerners and Filipinos, beheading victims and receiving large ransom payments. It was blamed for the bombing of a passenger ferry in 2004 which killed more than 100 people.
US-backed military offensives have considerably weakened the group to a few hundred rebels who are mostly on the run, according to the Philippine government.