Ten Indonesian sailors abducted by Abu Sayyaf Islamic militants were freed in the southern Philippines on Sunday after five weeks in captivity, Philippine police said.

Unknown men delivered the 10 tugboat crewmen to the home of provincial governor Abdusakur Tan Jnr on the remote island of Jolo during a heavy midday downpour, Jolo police chief Junpikar Sitin told AFP by telephone.

"The report (of their release) is confirmed. They were there. I saw them," Superintendent Sitin added.

The provincial police chief, Senior Superintendent Wilfredo Cayat, confirmed the release of the 10 Indonesians, but declined to give any details to AFP.

It came six days after Abu Sayyaf members beheaded a Canadian hostage, John Ridsdel, for whom the gunmen had demanded $21mn in ransom.

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

The authorities said the group were still holding 11 foreign hostages - four sailors from Indonesia and four others from Malaysia, a Canadian tourist, a Norwegian resort owner, and a Dutch bird watcher.

A consular official at Indonesia's Manila embassy, who gave his name as Tody, told AFP: "We cannot tell you any detail as of now. It's confidential."

In Jakarta, foreign ministry spokesman Arrmanatha Nasir told AFP: "Since this morning, the Indonesian foreign minister continued her coordination with her Filipino counterpart and our team on the field to confirm the information."

Radical offshoot  

The 10 sailors were abducted off the southern Philippines on March 26 as their tugboat pulled a barge from Borneo island to the Philippines.

Filipino authorities later described the kidnappers as members of the Abu Sayyaf, a small group of militants based on Jolo and nearby Basilan island and accused of kidnappings and deadly bombings.

The vessels' owners received a ransom call from someone claiming to be from the Abu Sayyaf militant group the same day.

However Sitin said he was unaware that any had been paid. Abu Sayyaf does not normally free hostages unless a ransom is paid.

Abu Sayyaf is a radical offshoot of a Muslim separatist insurgency in the south of the mainly Catholic Philippines that has claimed more than 100,000 lives since the 1970s.

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

The group is believed to have just a few hundred militants 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 gangs have earned many millions of dollars from kidnapping foreigners and locals since the early 1990s.

Although Abu Sayyaf's leaders have pledged allegiance to the Islamic State group, analysts say they are more focused on lucrative kidnappings-for-ransom than setting up a caliphate.

The surge of abductions has sparked calls by Indonesia for joint military patrols with Malaysia and the Philippines in the high seas where the Malaysian and Indonesian sailors were abducted.

Jakarta announced last week it plans to host a meeting of foreign ministers and military commanders from the three neighbours on the issue on Thursday.