Cotabato City, Philippines - Six people were killed and nine others wounded when a bomb exploded on Friday in front of a busy public market in a southern Philippine town.

The attack was believed to have targeted Andal Ampatuan, governor of Maguindanao province, authorities said.

The explosive was planted inside a passenger van, locally called a "multi-cab," which was parked near the market in Shariff Aguak town in Maguindanao province, 950km south of Manila.

"The bomb was detonated as the convoy of Governor Andal Ampatuan passed by," said Norie Unas, provincial administrator. "The empty multi-cab was totally destroyed.

"The governor was the main target," he added.

Ampatuan was unhurt in the attack, the fourth attempt on his life since 2001.

Senior Superintendent Akmad Mamalinta said one of the vehicles in the governor's 10-vehicle convoy was also destroyed, killing two aides, a niece and a close friend of Ampatuan.

The fifth fatality was a nephew of Maguindanao Congressman Simeon Datumanong, while a male civilian who was injured in the blast on his way to the market died later in hospital, he added.

Nine other injured victims were still confined in hospital.

Mamalinta said investigators had not yet identified suspects and were still determining the type of the improvised explosive device used in the attack.

Authorities warned Thursday of plots by Islamic militants to launch bomb attacks in Manila and other key cities in the southern Philippines. - Sapa-dpa