The United Nations refugee agency has called on Australia to find a humane solution to the plight of hundreds of refugees and asylum seekers living on Papua New Guinea's Manus Island.

The detention centre on the island was officially closed in October, but many of the asylum seekers refused to leave, fearing for their safety at alternative accommodation.

Staff at one of these facilities have been forced to leave by angry locals, who have blocked food deliveries.

Speaking at a UNHCR briefing at Geneva, Cecile Pouilly described the situation as critical.

"We are talking here about people who have suffered tremendously, extreme trauma, and are now feeling so insecure in the places where they are staying," she said.

"There are many victims of torture, people who have been deeply traumatised, having no idea what is going to happen next to them.

"In light of the continued perilous situation on Papua New Guinea's Manus Island for refugees and asylum seekers abandoned by Australia, UNHCR has called again this week on the Australian Government to live up to its responsibility and urgently find humane and appropriate solutions."

Ms Pouilly said that in the past four weeks, there had been at least five security incidents.

She added that although Papua New Guinea now had to deal with the situation, the buck should stop with Australia.

"What we clearly are saying is that it is Australia's responsibility in the first place," she said.

"Australia is the country that created the situation by putting in place this offshore processing facility. So what we are asking is for Australia to find solutions for these people."

Her comments came after refugees said they were running out of food because local landowners were blockading their accommodation.

Protesting landowners have been stopping staff, medicine and food deliveries from going in to the East Lorengau Transit Centre, where more than 300 men are kept, since December 19.

The blockade of trucks is preventing anyone getting in or out. ( ABC: Supplied )

Reuters/ABC