A Manus Island MP says he fears the release of asylum seekers and refugees from the detention centre may lead to violence.

Papua New Guinea immigration authorities said the 898 men in Australia's offshore processing centre on Manus Island are no longer in detention, because they can now visit the main town.

This is to comply with a Supreme Court ruling last month that found their detention was illegal.

The detainees on Manus Island say they now have the option to catch one of three buses into the main town each morning, but must sign agreements taking responsibility for their own safety.

They are not allowed to walk out of the centre, because it is on a PNG naval base.

They also say they may stay at an Immigration-run transit centre overnight.

But Manus MP Ronnie Knight said residents feared they would have to deal with unwanted behaviour, particularly from detainees harassing local women.

"There's been incidences already where we've had these people chasing young girls," he said.

The detainees say many of them are afraid to leave the centre, because they fear being attacked by locals.

Deputy Chief Migration Officer Esther Gaegaming said "no asylum seeker or refugee is in detention".

"We are continuing to work towards fully implementing the orders of the Supreme Court."

PNG's Supreme Court ruled on April 26 that detaining the men on Manus Island had breached their constitutional rights to personal liberty in Papua New Guinea.

'They are still controlling us'

Refugee Behrouz Boochani said the changes had not allowed true freedom of movement.

Sorry, this video has expired Eric Tlozek reports from PNG

"They are still controlling us," he said. "Even when we want to go from Oscar to Delta [internal compounds] we should give our ID cards to the officers.

"It means we are not free to walk."

Mr Boochani said the refugees and asylum seekers were still being separated inside the centre and refugees could not visit the compounds where men who were unsuccessful in their refugee applications were housed.

The men are only allowed to leave Manus Island if they sign an agreement to be resettled in PNG, and the ABC understands only eight men have done that.

Of those, three have returned to Manus Island, saying they had been robbed and threatened when they were resettled in Lae, and did not earn enough money to support themselves.

Two of those refugees were arrested upon returning to Manus Island, one for trying to get back into the transit centre for refugees and another for repeatedly asking for a phone and credit to call his family.

Another refugee remains in hospital in Lae after being violently robbed twice in two days.

Only three men are still working, while a fourth is about to start his new job.