Last asylum seekers exiting Manus Island

Just four asylum seekers are left in the immigration processing centre on Papua New Guinea's Manus Island.

Home Affairs Minister Peter Dutton said the centre would be closed down completely after those four men are sent to Port Moresby in coming weeks.

More than 630 refugees had gone to the United States under the deal where that country agreed to resettle up to 1250 of those who had come to Australia, he said.

"We have got the number of people that Labor put on Manus Island down to four," Mr Dutton told parliament on Tuesday.

"We have completely closed down the regional processing centre on Manus Island and we have done that because we don't have new boat arrivals."