The UN has suspended relief efforts in areas of Papua New Guinea worst hit by February’s earthquake after violence and instability made it unsafe for its workers.

More than 150 people died when a 7.5 magnitude earthquake struck the highlands region on 26 February, and 270,000 people are still in need of emergency aid – 125,000 of them children – according to the UN.

There are unconfirmed reports other non-government organisations have joined the UN in pulling out of Tari, in Hela province, as threats against aid staff and daily fighting between residents have made it too dangerous to continue.

Dr Luo Dapeng, speaking on behalf of the UN in Papua New Guinea, said: “The UN has temporarily relocated 12 UN non-essential relief workers from Tari to other locations due to the current security situation in the area, which is compromising our ability to implement relief activities.

“We aim to resume relief work as soon as the security situation allows.”

The Ministry of Foreign Affairs in New Zealand, which has so far committed NZ$3.5m ($2.5m) in aid funding as well as aircraft and personnel, said the outbreak of violence was adding extra pressure to relief efforts.

A full picture of the damage caused is only beginning to emerge now New Zealand Ministry of Foreign Affairs

“This is a challenging recovery effort for a number of factors, including the remoteness of affected areas, and the recent intensification of civil unrest that has hampered access for some frontline relief efforts for security reasons,” the spokesperson said. “A full picture of the damage caused is only beginning to emerge now. What is clear, though, is that the recovery will take some time.”

Road access to the affected regions of Hela, the Southern and Western Highlands remain unreliable or impossible, with all relief supplies having to be flown in by air, and then walked or driven to villages.

This week Orlena Scoville, head of Care Australia’s earthquake emergency team there, visited the villages of Huya, Walagau, Mougulu and Dodomona, and said aid delivery had “stagnated”.

Villages whose usual population was 300 have swollen to 2,000; with many of the new residents having little shelter or means of support, placing increased pressure on land and basic infrastructure.

According to the UN close to 20,000 are living in informal care centres, many of them no more than tarpaulin sheets pulled across wooden frames, while 143,127 have been deemed food insecure due to landslides wiping out their gardens and crops, especially the local staple of sago.

Areas affected by landslides are seen after a powerful 7.5 magnitude earthquake, in Hela, Papua New Guinea, in February. Photograph: Social Media/Reuters

Scoville said: “Food is definitely a major issue, there is not enough food, the villages I was in are mostly dependent on aid drop-offs. They have been saving food, because they don’t know where the next supply is coming from. It is definitely still an insecure situation.”

“The coping mechanisms people are using is they are restricting their food intake. People have had one or no meals a day; they are rationing out food as slowly as they can and not touching the food stocks they have because they don’t know when the next food supply is coming in.”

The remoteness of the region meant general health and well-being were further deteriorating due to a lack of medicines and supplies, and many people remaining in states of shock and grief, five weeks after the quake struck.

The Australian government has committed A$5m ($3.8m) in aid funding to the PNG government, which includes nine doctors who have treated more than 600 people at Mendi hospital in the Southern Highlands.

PNG’s prime minister, Peter O’Neill, said the long-term cost of the earthquake would run into the hundreds of millions of dollars, and short-term emergency relief efforts in Hela province alone were estimated at $60m.

Scoville said: “The biggest need going forward will be relocating these families back to a permanent area where they can re-establish their homes and gardens.

“Some people are looking at going back to their old areas, but a lot of people are going to have to resettle in new areas, so this is going to be a long process of recovery.”