MANILA (Reuters) - Soldiers have found the body of a German woman on an abandoned yacht in the troubled waters of the southern Philippines and suspect her companion may have been taken captive by Islamist Abu Sayyaf rebels, the military said on Monday.

The body was found naked and with gunshot wounds on the yacht which bore a German flag and was docked on a remote island in the Sulu archipelago, a stronghold of the Abu Sayyaf, an al-Qaeda linked group notorious for kidnapping and increasingly, piracy.

“A shotgun was found near her body,” army spokesman Major Filemon Tan told reporters. “We are verifying reports a German national ... was taken captive by the Abu Sayyaf.”

Tan said an Abu Sayyaf leader, Muamar Askali, had made claims on radio that they were holding a 70-year-old German after intercepting the yacht in Sabah, eastern Malaysia, last week.

Philippine President Rodrigo Duterte is due to hold talks with Malaysian Prime Minister Najib Razak this week, during which tackling Abu Sayyaf is due to figure as the two countries grow increasingly concerned about radicalism and lawlessness.

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.

Several hostages had been freed, after paying ransom to the Abu Sayyaf, a group known for kidnappings and beheadings, including two Canadians this year.

It is holding 15 captives, including a Netherlands citizen, five Malaysians, two Indonesians and seven Filipinos.