Two German tourists who were freed last month by Abu Sayyaf militants after six months of jungle captivity have helped investigators identify at least five of their captors, who will soon face criminal complaints, officials said Wednesday.

German cardiologist Stefan Viktor Okonek, 72, and Henrike Dielen, 47, were freed by the militants near mountainous Patikul town in southern Sulu province on Oct. 17, reportedly in exchange for a large ransom.

They told investigators that Okonek was threatened with death and beaten before they were set free. At one point, the Abu Sayyaf posted a picture online showing a masked militant aiming a long knife at the head of Okonek, who was kneeling on the ground beside Dielen.

The Germans identified the leaders of their kidnappers when they were shown pictures of Abu Sayyaf militants, police Senior Superintendent Roberto Fajardo said. Criminal complaints will be filed soon against the suspects, including Moammar Askali, a young rebel commander and spokesman who uses the alias Abu Rami, Fajardo said.

Askali told a local radio network that his group freed the Germans after receiving a 250 million pesos ($5.6 million) ransom.

The Abu Sayyaf, a loose grouping of about 400 mostly poor rural fighters, has turned to kidnappings for ransom, extortion and other crimes to endure years of battle setbacks dealt by U.S. military-backed Philippine offensives.

The extremist group had links to the al-Qaida terrorist network and is on a U.S. list of terrorist organizations for deadly bombings, kidnappings and beheadings.

In a written statement to investigators, a copy of which was obtained by The Associated Press, Okonek said Abu Rami told them they were kidnapped by the militants to seek a large ransom. Okonek said Abu Rami talked with the captive's family by telephone but he was unaware if any ransom was paid.

"I heard Abu Rami talking, demanding ransom for our release," Okonek said, adding that his captors hurt him a few days before they were set free.

"I was handcuffed, put in a hole or tied to a tree," Okonek said. "For almost three days, I was punched, kicked and one of the kidnappers even tried to break my left finger."

The Germans said they were abducted while traveling on their yacht from western Palawan province to the Malaysian state of Sabah to have their vessel repaired. Ten gunmen, who introduced themselves as policemen, approached, boarded their yacht then tied their hands, they said.

Philippine troops have launched a search for the kidnappers in Sulu's jungles but have yet to find them.