MANILA, Philippines - Philippine warplanes on Thursday attacked Islamic militants holding 20 foreign hostages on a remote southern island, but there was no sign of the captives, the military said.
Government forces said they rained artillery fire on Abu Sayyaf gunmen on a mountainous area of Jolo island, as planes and helicopters flew low over the jungle terrain dropping bombs.
President Benigno Aquino on Wednesday vowed to "neutralise" the militants, who have declared allegiance to the Islamic State group, a day after the severed head of Canadian hostage John Ridsdel was dumped near Jolo's city hall.
"As a result of the bombardments... they were able to occupy the former places occupied by the Abu Sayyaf that resulted in the recovery of (Ridsdel's) torso," military spokesman Colonel Noel Detoyato told reporters in Manila.
He said local civilians told authorities that 14 gunmen were killed, but no bodies were reported to have been discovered and his tally could not be independently verified.
Detoyato said the offensive, targeted at veteran one-armed Abu Sayyaf commander Radullan Sahiron, was proving a success.
"What is important here is that operations are continuing and we are gaining headway and our troops are determined," Detoyato said.
However he said there had been no sightings of the remaining hostages, and that the militants had apparently escaped the area that had been the target of the attacks.
Aquino said Wednesday the hostages, including a Canadian, a Norwegian and a Filipina abducted with Ridsdel from yachts at a southern Philippine marina seven months ago, were being held by Sahiron on Jolo.
The militants are also holding 18 Indonesian and Malaysian sailors kidnapped from waters south of the Philippines over the past month, as well as a Dutch bird watcher abducted in 2012.
The 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.
It 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 the Abu Sayyaf's leaders have pledged allegiance to Islamic State, analysts say they are mainly focused on their lucrative kidnappings-for-ransom rather than setting up an Islamic caliphate.
The Abu Sayyaf is also blamed for deadly bombings, including an attack on a ferry on Manila Bay in 2014 that claimed 116 lives in the country's deadliest terror attack.
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