Two Indonesian sailors believed to have been abducted by Islamist militant group Abu Sayyaf in the Philippines escaped today after almost two months in captivity, the military said.

Mohammad Safyan and a second hostage identified only as Ismail were found separately in Luuk town on Jolo Island, 1,000 kilometres south of Manila, regional military spokesperson Major Filemon Tan.

Safyan was found first, floating and trapped in fish netting in a mangrove area in Luuk, Tan said.

“The victim escaped when his captors declared that they would behead him,” he added.

Hours later, soldiers found Ismail in the same area, Tan said.

They were among seven Indonesian crew members abducted on June 20 while their boat was sailing back to the Indonesian province of East Kalimantan from the Philippine city of Cagayan de Oro.

Three other Indonesian fishermen are believed to have been abducted by Abu Sayyaf militants off the southern Philippines in mid-July.

Abu Sayyaf, which has been blamed for some of the deadliest terrorist attacks in the Philippines, is also suspected of holding captive five Malaysian crew, a Norwegian, a Dutchman and four Filipinos on Jolo.

The militants beheaded two Canadian hostages in April and June after a ransom was not paid for their freedom.

Philippine President Rodrigo Duterte has directed the military to crush Abu Sayyaf and also warned that the group could be a source of recruitment for the Islamic State extremist group.

On Monday, Duterte denounced Islamic State for its “barbaric practice” and warned the group he would never allow them to destroy the Philippines.

“They don’t have any political ideology,” he said. “You maim people, you kill them. Women who refuse to have sex with them, they simply burn them.”

- dpa