A powerful explosion killed at least two people and wounded 54 others in a southern Philippine port city that has been hit by similar blasts blamed on Muslim militants, police said Saturday.

The blast occurred at a bar across the street from a busy bus terminal in Zamboanga city, damaged nearby establishments and hitting the victims with flying glass and debris. One officer was among the wounded, police said.

Police suspected the militant Abu Sayyaf group, which operates in Zamboanga and nearby provinces, saying the attack could have been in retaliation for the foiled prison escape of a brother of one of the group's leaders.

Earlier this week, army special forces killed at least three Abu Sayyaf gunmen in running gunbattles and have continued to pursue the militants in nearby Basilan province. The group has previously set off bombs to divert attention from military operations.

Regional police chief Edwin Basbas said investigators were looking for three men who were seen in the vicinity shortly before the blast.

Zamboanga police information officer Alex Mabalot said the blast killed a motorcycle taxi driver and another man who succumbed to his wounds. Only 10 people remained in hospitals, he said.

The bar and the bus terminal had been separately hit several years ago by bomb blasts blamed on the Abu Sayyaf. At least two suspected militants were arrested in another bomb attack near a police station last month, he said.

The Abu Sayyaf numbers about 300 fighters and remains a major security threat in the country's south despite U.S.-backed Philippine military offensives.