MANILA (Reuters) - Gunmen abducted six Vietnamese sailors and shot another on Friday when a bulk carrier was intercepted in Philippine waters off a southern island stronghold of the militant Abu Sayyaf group, the coastguard said.

The cargo ship was bound for Davao City in another part of the province of Mindanao, but was intercepted when passing through a strait off Basilan island by 10 armed men who came aboard and took hostages.

"One of the crew was shot and was evacuated to a local hospital," said Commander Jerome Cayabyab of the coastguard.

He said the fate of the captives were uncertain after they were transferred to smaller, faster boats. It was the second kidnapping incident in the south in a week.

The Abu Sayyaf, a militant group that swears allegiance to Islamic State, said on Monday it kidnapped a German national. The military said a woman found dead in an abandoned yacht off an island near Basilan was believed to be his female companion.

The latest attack on commercial shipping occurred just hours after the leaders of the Philippines and Malaysia agreed to step up maritime cooperation in their borders to stop the piracy.

Abu Sayyaf rebels have since March been intercepting slow-moving tug boats towing coal barges in waters near the borders of Malaysia and the Philippines, taking captive more than a dozen Indonesian and Malaysian sailors.

Though the group officially has a separatist, Islamist agenda, it has become better know for banditry and tactics that have proved highly effective, and earned large sums of money.

Several hostages had been freed, but experts say in those cases it is almost certain ransoms were paid. Abu Sayyaf has beheaded two Canadian hostages this year.

It currently has 16 captives, including a Netherlands citizen, a German, five Malaysians, two Indonesians and seven Filipinos.

Vietnam's foreign ministry did not immediately respond to a request for comment on the missing sailors.

(Reporting By Manuel Mogato; Editing by Martin Petty and Michael Perry)