Papua rebels hold guns to New Zealand pilot's head in chilling new video warning their hostage will be executed if their demands are not met in two months

Separatist rebels in the Indonesian region of Papua have released a chilling video  of them holding guns to the head of a captive pilot.

Philip Mark Mehrtens, a 37-year-old from New Zealand, will be executed if the demands of the rebels are not met in two months, the rebels said.

Mehrtens has been held by the group for the past ten months after he was kidnapped in February by West Papua Liberation Army (TPNPB) fighters.

He was working for an Indonesian aviation company when he was abducted after landing his single-engine Susi Air plane on a remote airstrip in the mountainous province of Nduga, found in Indonesia's western half of New Guinea.

In the intense 48-second clip circulating on social media, Mehrtens is seen sitting in a field, arms on his knees, surrounded by a ring of men pointing automatic rifles at him.

The leader of the group, seen wearing a Union Jack bandanna, is shown pointing his assault weapon at the New Zealander's head as he address the camera.

TPNPB's leader, named as Egianus Kogeya by Indonesian outlets, tells the camera that Mehrtens will be shot dead within two months if their demands are not met.

The group, designated a terrorist organisation by Indonesia, has in the past called for Papua to gain self rule from Indonesia.

New Zealand's foreign ministry (MFAT) said it was aware of the video. 

However, it did not release any other information concerning the footage, such as when or where it was filmed.

Efforts to secure the pilot's release were on-going, the government said, including working closely with Indonesian officials and New Zealand consulate staff.

MFAT added that Mehrtens's wellbeing was the top priority, and that his family in New Zealand were being kept updated on the situation and supported.

In April this year, TPNPB fighters killed six Indonesian fighters who were part of a force that attempted to rescue Mehrtens from captivity.

Military leaders had narrowed down the New Zealander's location but were attacked by the rebel group on April 15.

Military reports stated at least six people died, and 21 others fled into the jungle.

It was reported at the time that one soldier fell into a deep ravine and died, while others came under attack trying to rescue him. 

The new video is not the first time TPNPB has threatened to execute Mehrtens.

Day after he was captured, the group said in another, similar video, that he 'will die here' like 'the rest of us' if the Indonesian army tried to rescue him.

Rebel separatists' spokesperson Sebby Sambom wrote on Facebook that Mr Mehrtens will be held hostage for negotiations with Indonesia - but warned that if Jakarta refused to negotiate or intervened militarily then the pilot 'will be executed'. 

Sambom said at the time that the rebels would 'never release' Mr Mehrtens unless Jakarta made the Papua region independent from Indonesia.

But the Indonesian government stood firm, saying Papua will 'forever remain a legitimate part' of Indonesia.

Mr Mehrtens met his wife Maria in Indonesia, with the couple moving to New Zealand and living in Auckland while Mr Mehrtens worked for Jetstar.

The couple then returned to live in Indonesia when he recommenced employment with Susi Air, founded in 2004, which operates a fleet on 50 aircraft.

Separatist rebels kidnapped him after they stormed a single-engine Indonesian Susi Airlines plane shortly after it landed on a small runway in February.

He was scheduled to evacuate 15 construction workers building a health centre in the district after the separatist rebels threatened to kill them.

'Our plan to evacuate the workers angered the rebels, who responded by setting fire to the plane and seizing the pilot,' said Nduga district chief Namia Gwijangge, who was one of the passengers. 'We deeply regret this incident.'

The rebels released all five passengers because they are indigenous Papuans, rebel spokesman Sebby Sambom said at the time.

Flying is the only practical way of accessing many parts of the mountainous area. 

Papua - which encompasses the western half of New Guinea (with Papua New Guinea making up the eastern half) - was incorporated into Indonesia in 1969 after an UN-sponsored referendum widely seen as problematic.

Since then, a low-level insurgency has simmered in the mineral-rich region, which is divided into two provinces, Papua and West Papua.

Around one million people live in Papua, including some uncontacted people.