MANILA - Gunmen in southern Philippine waters killed one crewman of a Vietnamese vessel and abducted seven in what appeared to be the latest attack by pirates in the area, the Philippine coastguard said on Monday.

Coastguard and marine soldiers rescued 17 Vietnamese who were part of the 25-man crew of MV Giang Hai, which was attacked on Sunday evening near Baguan Island in Tawi-Tawi, an area close to the stronghold of the notorious Abu Sayyaf militant group.

An investigation was underway and the coastguard had launched a pursuit in coordination with the military and police, said coastguard spokesman Commander Armand Balilo.

Well armed and equipped with fast boats and high-tech navigation devices, the Abu Sayyaf is a stubborn problem for the Philippine military, which has failed to curtail piracy and kidnappings in the area, despite major troop deployments in the in the Sulu Archipelago.

The Islamic State-linked group has been involved in frequent acts of piracy and has beheaded captives when ransom demands have not been met.

Before the latest attack, the militants were holding 27 hostages, according to a tally of reports about kidnappings and a few releases.

The captives are Indonesian, Malaysian and Vietnamese seamen, as well as Filipinos, a Dutchman, a German and a Japanese national.

A surge in piracy off parts of the Philippines is forcing ship-owners to divert vessels through other waters, pushing up costs and shipping times.

President Rodrigo Duterte said last month he had asked China for help in the fight against the militants by sending ships to patrol the dangerous waters.

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