President Rodrigo Duterte vowed sustained operations against the Abu Sayyaf Group after a German national was reported beheaded after a ransom of P30 million was not paid on Sunday.

"It’s a sustained military action that is needed there," Duterte told reporters on Monday regarding the Abu Sayyaf problem.

In a separate statement, Presidential Adviser on the Peace Process Jesus Dureza said the government grieves and strongly condemns the barbaric beheading of kidnap victim German Juergen Gustav Kantner in Sulu.

"Up to the last moment, many sectors , including the Armed Forces of the Philippines exhausted all efforts to save his life. We all tried our best. But to no avail," he said.

"I was always in close contact with German authorities in our efforts. We condole with his family, friends and loved ones," Dureza said.

A one-minute 43 second video which appears to confirm Sunday’s execution of a German by the Abu Sayyaf has spread in the internet, but a military spokesman said he “will not dignify the video by watching it.”

"Video is not enough basis to become confirmatory for... beheading," said Brig. Gen. Restituto Padilla.

Col. Edgard Arevalo, AFP Public Affairs chief, said the Moro Islamic Liberation Front (MILF) are helping the government in verifying the reported execution of Kantner.

Padilla said confirmation includes “any compelling evidence such as the identifiable remains of a victim, body parts that can be subjected to DNA, confirmatory testing or a trusted eye witness account.”

It can be recalled that earlier this month a video of Kantner also spread online, it stated 30 million pesos ransom demanded by his abductors for his release.

Kantner and his companion Sebine Isle Merz when he was abducted by the terrorist group in October 2016 while Merz was found dead inside their yacht in Sulu.

Arevalo said based on their latest record the Abu Sayyaf is holding a total of 33 kidnap victims and 26 are foreigners. Celerina Monte, Robina Asido/DMS