Ten Indonesian sailors abducted by Abu Sayyaf fighters have been freed in the southern Philippines after five weeks in captivity, local police said.

Unknown men dropped off the 10 tugboat crewmen at the home of provincial governor Abdusakur Tan Jr on the remote island of Jolo on Sunday, Jolo police chief Junpikar Sitin told the AFP news agency.

"The report [of their release] is confirmed. They were there. I saw them," Sitin said.

The condition of the former captives was not immediately known, though Sitin said the group ate lunch at the governor's home.

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They were abducted on March 26 by fighters described by Philippine authorities as members of the Abu Sayyaf, an armed group based in Jolo and nearby Basilan island which is accused of kidnappings and deadly bombings.

Jolo's mayor, Hussin Amin, welcomed the release of the Indonesians, but said he was unaware whether a ransom had been paid.

"If this big release came in exchange for money, those who paid are supporting the Abu Sayyaf," he said.

"This money will be used to buy more firearms and will be utilised as mobilization funds by these criminals."

Abu Sayyaf does not normally free hostages unless a ransom is paid, which is the group's main source of funding.

Canadian beheaded

The Indonesians were freed six days after Abu Sayyaf members beheaded a Canadian hostage, John Ridsdel, after their ransom demand was not met.

Canadian Prime Minister Justin Trudeau said he was outraged by the death of Ridsdel, a former mining executive, calling it an act of "cold-blooded murder".

Philippine President Benigno Aquino vowed on Wednesday to "neutralise" the fighters after Ridsdel's decapitated head was left outside a government building on Jolo.

Authorities said the group is still holding 11 other foreign hostages - four Indonesians, four Malaysians, another Canadian, a Norwegian, and a Dutchman.

It is believed that the armed group have only a few hundred members but has withstood repeated US-backed military offensives against it, surviving by using the mountainous, jungle terrain of Jolo and nearby islands to its advantage.

Abu Sayyaf violence has claimed more than 100,000 lives since the 1970s.

Source: Agencies