Zamboanga City, Philippines - Three Filipino public school teachers were seized Friday by unidentified gunmen off a southern Philippine city, a regional police chief said.

Chief Superintendent Angelo Sunglao said the victims were riding a passenger boat near Zamboanga City, 875 kilometres south of Manila, when the gunmen seized them Friday morning.

Sunglao said the gunmen who were riding on a separate motorized boat, boarded the passenger vessel and seized the three victims.

"The gunmen did not harm the other passengers," he said.

Sunglao said investigators were still trying to determine the motive behind the kidnappings and the identity of the gunmen.

The latest kidnapping occurred as government forces continued to scour the nearby island of Jolo in search of the three staff of the International Committee of the Red Cross (ICRC), who were seized by Muslim militants a week ago.

Swiss Andreas Notter, Italian Eugenio Vagni and Filipino Mary Jean Lacaba had just visited the provincial jail in Jolo when Abu Sayyaf rebels seized them on January 15. (dpa)