The UN Human Rights Commission (UNHRC) has denounced the Australian government for withdrawing support to former Manus Island detainees as the stand-off over the provision of services to more than 600 men entered its fifth day on Saturday.

It comes as the detainees have called for an investigation into the death of a 29-year-old asylum seeker, who was killed in a road accident on the island nation on Thursday, reports the Guardian.

In a statement, Rupert Colville, spokesman for high commissioner Zeid Ra’ad Al Hussein, said the UN’s human rights committee had “serious concerns about the welfare, safety and wellbeing” of the men who remained at the centre in Papua New Guinea, which was formally decommissioned on Tuesday.

Water to the centre and essential medical services were also cut off on Tuesday, while electricity was disconnected on Wednesday morning. The men have been digging for water.

Colville said the men were “too frightened to leave”, the Guardian reported.

“We call on the Australian government, as the party who interned the men in the first place, to immediately provide protection, food, water and other basic services which have been cut off since authorities shuttered the facility on October 31.”

The Commission repeated its criticism that Australia’s offshore refugee processing regime was “unsustainable, inhumane and contrary to its human rights obligations” and said asylum seekers and refugees should be immediately transferred to Australia for processing.

Rallies in support of the Manus refugees were held in Canberra and Brisbane on Friday and planned for Melbourne and Sydney on Saturday.

On Friday, opposition leader Bill Shorten urged Prime Minister Malcolm Turnbull to accept a renewed offer from New Zealand to take 150 refugees from Australia’s offshore processing camps.