Updated February 28, 2017 12:08:53

Abu Sayyaf extremists in the Philippines have released a video showing the beheading of a German hostage in the first sign the brutal Filipino militants carried out a threat to kill him after a ransom deadline lapsed over the weekend.

President Rodrigo Duterte's adviser dealing with Muslim rebel groups, Jesus Dureza, said the Philippines military and other groups "exhausted all efforts" to save Jurgen Gustav Kantner, up to the final moment.

"We grieve as we strongly condemn the barbaric beheading of yet another kidnap victim," Mr Dureza said in a statement.

"We all tried our best. But to no avail."

The brief video circulated by the SITE Intelligence Group, which monitors jihadi websites, showed Mr Kantner sitting in a grassy clearing, saying: "Now he kill me" before a masked militant beheaded him with a curved knife.

A few gunmen muttered "Allahu Akbar", the Arabic phrase for "God is great", in the video that lasted nearly two minutes.

The Philippines military confirmed Mr Kantner had been "mercilessly and inhumanly murdered".

"Our operations in the past several days and nights, using all our resources, were unrelenting," spokesman Colonel Edgard Arevalo said in a statement.

Photo: Soldiers search for members of extremist group Abu Sayyaf. (Reuters: Marconi B Navales, file)

"We lost some of our best men in the process, because we value the life of Mr Kantner and that of the others who have fallen prey to this terrorist group."

An intelligence report seen by The Associated Press said an Abu Sayyaf militant, Moammar Askali, had wanted Mr Kantner to be killed as announced, but others wanted to wait out for a ransom payment.

The militants circulated a video earlier this month in which Mr Kantner said he would be killed if ransom was not paid by 3:00pm on Sunday.

Philippines officials have said the militants were seeking a ransom of 30 million Philippine pesos ($778,000).

In Germany, Chancellor Angela Merkel condemned, "this abominable act, which shows once again how inhumane and without conscience these terrorists act", spokesman Steffen Seibert said in a statement.

"We must all stand together to fight against them."

German foreign ministry spokesman Martin Schaefer would not give any details on possible negotiations with the kidnappers, including whether there was a ransom demand, citing government policy and saying, "Public comment never helps in finding a solution" in such cases.

Woman sailing with hostage killed last year

The Abu Sayyaf claimed in November its gunmen had kidnapped Mr Kantner and killed a woman sailing with him off neighbouring Malaysia's Sabah state.

Villagers later found a dead woman on a yacht with the German flag off Laparan Island in Sulu province in the southern Philippines, the military said.

Photo: Canadian man Robert Hall was beheaded by Abu Sayyaf last year.

Mr Kantner and his partner, Sabine Merz, had been taken hostage by Somali pirates in 2008 and later freed, officials said.

The Abu Sayyaf, which the US and the Philippines have blacklisted as a terrorist organisation, is holding more than 20 foreign and local hostages in jungle encampments in the country's south.

They beheaded two Canadian men last year after separate ransom deadlines lapsed.

Mr Duterte has ordered troops destroy the Abu Sayyaf extremists, saying their ransom kidnappings were embarrassing and were creating a security alarm in the waters bordering the south, Malaysia and Indonesia.

The three countries have made efforts to jointly shore up security along their busy sea border, but the kidnappings by the Abu Sayyaf and allied gunmen of passing crews have persisted.

AP

Topics: unrest-conflict-and-war, terrorism, philippines, germany, asia

First posted February 28, 2017 10:36:29