MANILA (Reuters) - Philippine troops raided an Islamist militants’ camp on a remote southern island and rescued a Vietnamese sailor held captive for nine months, a navy spokeswoman said on Monday.

More than 20 people, including 14 foreigners, are being held by pro-Islamic State militants Abu Sayyaf on two islands in the south, some of them for as long as three years.

Do Trung Huige, 33, was left behind when troops attacked an Abu Sayyaf camp on Mataja island on Saturday, Jesca May Viduya, spokeswoman for the Western Mindanao naval forces, said.

“There was no firefight because his captors abandoned him as troops approached,” she said, adding the sailor was abducted with five others in November by militants who attacked a cargo ship.

Two Vietnamese sailors are still being held, two were beheaded and another was rescued. On nearby Jolo island, two Vietnamese sailors were among 19 captives still being held in a separate abduction.

The Abu Sayyaf group is notorious for bombings, beheadings, extortion and kidnap-for-ransom in the south of the mainly Roman Catholic country.

One of its leaders, Isnilon Hapilon, has been blamed for planning the occupation of a mainly Muslim city in the south.

More than 700 people have been killed and 400,000 displaced in the three-month battle to retake Marawi City which has yet to end.