Cotabato City, Philippines  - Philippine police on Wednesday defused two homemade bombs found inside a passenger bus in the country's troubled south, officials said.

The bombs, made from 81-millimetre and 60-millimetre mortar shells, were hidden in abandoned baggage inside the bus in Isulan town, Sultan Kudarat province, 930 kilometres south of Mnaila.

Police Superintendent Suharto Teng Tucao said bomb experts removed the explosives from bus and safely defused them.

"Passengers immediately got off the bus after they discovered the baggage containing explosives," he said. "We are thankful the explosives were recovered before they exploded."

The bus, which was carrying some 40 passengers, was allowed to travel after the bombs were removed.

No suspects have been identified in the bombing attempt. Previous bomb attacks on passenger buses in the southern region of Mindanao have been blamed on extortion groups.

The attempt came amid heightened alert in Mindanao following bombings on two department stores in nearby Iligan City earlier in the month, killing three people and injuring more than 40.

On Tuesday evening, a suspected bomb courier was killed and a police officer was wounded when a homemade bomb planted in a tricycle exploded in Esperanza town, also in Sultan Kudarat.

Police said they suspect the Moro Islamic Liberation Front, the largest Muslim rebel group fighting for an independent Islamic state since 1978, could be involved in the Esperanza blast. (dpa)