Nine people were killed yesterday when Philippine government forces clashed with suspected Abu Sayyaf militants in Bohol, an island province popular with tourists, sparking concern that the group may be diverting its kidnapping activities to the central Philippines.

Colonel Edgard Arevalo, the military's public affairs chief, said three soldiers and a policeman were killed when their team encountered about a dozen heavily armed bandits on three boats at around 5am in Inabanga town in Bohol province.

He said the bodies of five militants were recovered, along with firearms and an improvised explosive device.

Military spokesman Restituto Padilla said in a television interview: "From the firearms we recovered, it appears they were intending to cause trouble in the area."

Bohol and neighbouring Cebu province are popular holiday destinations for tourists, especially around this time of the year.

The clash occurred just days after the United States Embassy warned Americans against travelling to Cebu and Bohol owing to "unsubstantiated yet credible information" of terror threats in the area.

The second leg of Asean's ministerial meetings is set to be held in Bohol from April 19 to 22.

A raw intelligence report said the three boats were spotted leaving the Abu Sayyaf's stronghold in the Sulu archipelago. The report suggested that the Abu Sayyaf, known for profiting from kidnapping tourists, fishermen and sailors, may be venturing farther north from Sulu.

This is the farthest the Abu Sayyaf has been sighted from its Sulu base in the south, suggesting that navy patrols in waters separating Sulu and Sabah in Malaysia may be forcing the group to venture farther into the central Philippines.

Bohol is a a short 30-minute boat ride away from the major port city of Cebu.

The militants have been spotted before in Palawan province, which lies nearer to Sulu than Cebu and Bohol. In 2001, they seized three Americans and 17 local tourists from a high-end resort off Puerto Princesa city in Palawan.

The militant group, which has sworn its allegiance to the Islamic State in Iraq and Syria (ISIS), has become better known for banditry.

Since it turned kidnapping into a lucrative trade, the group has already beheaded an American, a Malaysian, two Canadians and a German.

It was behind several kidnappings in Sabah. Last month, five Malaysian sailors, abducted last July, were rescued.

Abu Sayyaf leader Isnilon Hapilon, said to be the head of ISIS in the Philippines, may have been killed in an air raid two months ago, President Rodrigo Duterte said recently.