The Philippines and Germany are condemning the beheading of an elderly German captive by Islamic State-linked Abu Sayyaf militants who posted a video of the killing after a deadline for a $US600,000 ($A781,140) ransom passed.

The video showed a machete-wielding militant behead Jurgen Kantner.

The German had appealed for help twice in short video messages, saying he would be killed if ransom were not paid.

You can watch one of them from YouTube here: it does not show the beheading.

On Monday, Jesus Dureza, presidential adviser on the Philippine peace process, said officials had exhausted all efforts to save Mr Kantner, 70, who was held on the tiny southern island of Jolo.

He made no mention of the ransom demand.

Philippines Foreign Minister Perfecto Yasay says Mr Kantner may have been killed because he was sick.

Speaking on the sidelines of the UN Human Rights Council in Geneva, he said the Philippines was seeking technological help from its allies to pinpoint the locations of remaining hostages and would stick to its tough “no ransom” policy.

“We will undertake our operations to make sure we give a premium to saving the lives of the hostages and precisely because of this our task has not been easy but we are prepared to crush them when the opportunity comes,” he told reporters on Monday.

The Philippines’ armed forces pledged in a separate statement to bring Mr Kantner’s killers to justice and to continue operations to free other hostages held by Abu Sayyaf.


German sailor Jurgen Kantner and his wife Sabine Merz pictured in 2009 in Berbera, a Somali port on the pirate-infested Gulf of Aden. Photo: Mustafa Abdi/AFP/Getty

In Berlin, Chancellor Angela Merkel called for a united international front against terrorism.

“The chancellor condemns this hideous attack that shows, once again, how unprincipled and barbarous terrorists act,” her spokesman Steffen Seibert said.

Last year Abu Sayyaf decapitated two Canadians on Jolo but later freed their two companions, a Filipino woman and a Norwegian.

The four had been seized from a tourist resort.

The ransom demand for the Canadians was $US6.4 million each.

Abu Sayyaf’s activities in recent years have been mainly banditry, but the Philippines believes Islamic State has been in contact with members of the group’s leadership with a view to gaining a foothold in Southeast Asia.

Kantner and his companion were taken captive in November while sailing near Sabah, eastern Malaysia, and brought to Jolo.

His companion was shot dead when she tried to resist the militants.

Reports of Mr Kantner’s execution emerged on Sunday evening, but the military only confirmed the killing on Monday, citing “reliable sources”.

Abu Sayyaf is currently holding 26 hostages – 13 Vietnamese, seven Filipinos, a Dutch national, a Japanese, two Indonesians and two Malaysians, the military said.

– Manuel Mogato