Joining a group of fellow recipients of the Australian of the Year award, the Canberra-resident has signed an open letter to Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten, urging them to address the growing crisis in the decommissioned Australian immigration detention centre.

Papua New Guinea police sealed off the camp on Thursday and ordered asylum seekers to leave the area after a group of about 380 men shut themselves inside for more than three weeks.

A small number of asylum seekers were arrested by local police.

Signatories to the new letter include domestic violence campaigner Rosie Batty, television personality Ita Buttrose, businessman Simone McKeon, Indigenous leader Mick Dodson and surgeon Fiona Wood.

Mr de Castella, who won the award in 1983 and went on to found the Smart Start for Kids program, said he was moved to take action by mental health campaigner and 2010 award recipient Patrick McGorry.

"I haven't done a straw poll so I don't know how the majority of Australians feel," he said.

"All I know is it's a bit of a disgrace for us as a proud nation, that has founded ourselves in strong moral positions, to have this issue, which has been allowed to grow and develop so much.

"I know there is no easy solution to it but I think it is important that we find a way to address Manus Island and resolve it in a much more humanitarian and fair way."

The group called for the government to send aid to the former detention centre, which has been without running water and electricity for more than a week.

Writing before police moved in, they warned it was inevitable people would become sick and even die because of the lack of basic sanitation, food, water and medical care.

The Commonwealth Games champion and former director of Canberra's Australian Institute of Sport said the federal government should resolve the situation as soon as possible and provide adequate medical treatment.

"I don't want to get involved in trying to make recommendations as to what the policy and the final decisions should be.

"What I'm concerned about is the fact the situation has gone to a point where there's a lot of suffering and a lot of issues being raised by people there.

"As I understand it, the offer from the Australian Medical Association to provide medical treatment and support the men on Manus has been declined," he said.

Mr Turnbull said transit centre the government wants detainees to move to had adequate facilities, food, water, security and medical services.

"They think this is some way they can pressure the Australian government to let them come to Australia. Well, we will not be pressured," he said.