Plainclothes policemen were deployed Saturday on privately-owned passenger buses hit by a series of bomb attacks in the southern Philippines, an official said, according to dpa. Chief Superintendent Felizardo Serapio said police marshals were deployed on all Weena passenger buses plying the provinces of Cotabato and Davao in the strife-torn region of Mindanao to prevent further attacks. "Starting today there will be plainclothes marshals in each of the company's buses," he said. "Our priority is always the safety of the passengers." The deployment of plainclothes policemen came after nine people were killed Friday when a homemade bomb exploded inside a Weena passenger bus in Bansalan town in Davao del Sur province, 990 kilometres south of Manila. The ill-fated bus had just left a public terminal in Bansalan when the explosion occurred. A second Weena Bus was also bombed in Cotabato City less than an hour before, but no injuries were reported. The passengers had already gotten off when the bomb exploded. Friday's twin bombings on the Weena passenger buses was the fourth in less than a month. On June 8, an improvised explosive device ripped through a Weena bus parked in a public terminal in Matalam town in North Cotabato province, injuring 10 people. On May 18, a homemade bomb exploded on a store inside Weena bus terminal in Cotabato City, killing three people and wounding more than 35 people. The Weena Bus company has been a target of bomb attacks allegedly perpetrated by extortionists. -- SPA