MANILA • Philippine President Benigno Aquino vowed yesterday to launch a military assault aimed at "neutralising" the Abu Sayyaf militants who beheaded a Canadian hostage and are holding more than 20 other foreigners.

"Casualties are to be expected. But what has to be of utmost importance is neutralising the criminal activities of the ASG," he said in a statement, referring to the Abu Sayyaf Group.

Mr Aquino released the statement after the severed head of Canadian John Ridsdel, kidnapped seven months ago from aboard a yacht, was dumped on Monday on a street on Jolo, a remote southern island that is one of the Abu Sayyaf's main strongholds.

"This murder was meant to terrorise our whole population. The Abu Sayyaf thought they could instil fear in us. Instead, they have galvanised us even further to ensure justice is meted out," he said.

"We have always been open to talks with those who desire peace, but those who commit atrocities can expect the full might of the state." He did not give a time frame for the assault.

Abu Sayyaf militants, whose leaders have pledged allegiance to the Islamic State in Iraq and Syria group, are holding more than 20 foreigners captive. They include another Canadian and a Norwegian man who were abducted at the same time as Mr Ridsdel at a marina near Davao, the biggest city in the southern Philippines. A Filipina was kidnapped as well.

The group is also believed to be holding a Dutch birdwatcher kidnapped from a southern Philippine island in 2012, as well as 14 Indonesian and and four Malaysian sailors abducted over the past month.

Mr Aquino said the captives were under the control of Radullan Sahiron, one of the Abu Sayyaf's founders who is famous for losing one arm in a battle against the military.

He said Sahiron had consolidated his forces around himself and the captives in Sulu, a small Muslim-populated archipelago about 1,000km from Manila. Jolo is the biggest island in Sulu. The Abu Sayyaf 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 the southern islands to its advantage.

AGENCE FRANCE-PRESSE