Zamboanga City, Philippines - Four police officers, including a provincial chief, were killed Thursday in a clash with Muslim militants holding captive an Italian Red Cross worker in the southern Philippines, police said.

Four police officers were also injured in the firefight in Maimbung town on Jolo island, 1,000 kilometres south of Manila, said Chief Superintendent Bensali Jabarani, a regional police director.

The clash erupted when Muslim Abu Sayyaf rebels attacked a group of police officers conducting a clearing operation after troops raided a guerrilla camp at the borders of Kulasi and Bulabog villages, Jabarani said.

Senior Superintendent Julasirim Kasim, police chief of Sulu province, which includes Jolo island, was leading the police officers in the operation. He and four officers were killed in the fighting.

Before his death, Kasim led police officers in capturing at least six Abu Sayyaf camps in operations aimed at freeing Italian Eugenio Vagni, a Red Cross worker held captive by the guerrillas for almost four months.

Vagni, who was reportedly suffering from a hernia injury, was abducted with two other colleagues - Swiss Andreas Notter and Filipino Mary Jean Lacaba - on January 15 after visiting the Jolo provincial jail to oversee a water and sanitation project.

The rebels freed Lacaba April 2 and Notter April 17.

Governor Abdusakur Tan has authorized a rescue operation to free Vagni, but the mission has been hampered by lack of accurate information on the location of the hostage and his captors.

The government has offered a 500,000-peso (10,256-dollar) reward for information on his whereabouts.

The Abu Sayyaf is the smallest but most violent Muslim rebel group in the southern Philippines. It has been blamed for some of the worst terrorist attacks and high-profile kidnappings, including the abductions of foreigners. (dpa)