At least 23 men were told on Wednesday morning they would receive bridging visas and be released from the Park Hotel in Carlton.

Still more were expected to depart the Melbourne Immigration Detention Accommodation (MITA) centre at Broadmeadows.

Kurdish refugee Mostafa Azimitabar, who is held at the hotel, tweeted just before 11am: "Breaking: Twenty six refugees who were locked up in the Park prison have got their Bridging Visa right now. Congratulations!!!"

Abdollah Sheikhi Pirkohi, another refugee detained in the hotel, confirmed to AAP the men had been taken to MITA to collect their possessions ahead of release.

Around 35 men are still detained at the hotel, he said.

The Melbourne hotel and another in Brisbane were designated as alternative places of detention by the federal government.

The men held in them were brought to Australia for medical treatment under the now-repealed 'medevac' legislation. Many have been in detention for over a year, some up to 18 months.

The hotels have been the centre of fierce protests during the past year.

Lawyer Noeline Harendran, of Sydney West Legal, believes the releases stem from habeas corpus cases she and colleague Daniel Taylor have filed on behalf of the men in federal courts.

The pair have lodged over 100 cases on behalf of the detained medevac refugees, arguing no purpose to their detention.

Seven of their clients were released in December.

Many but not all the men released on Wednesday had similar pending cases, with court dates in February, Ms Harendran said. "We've been working day and night, no Christmas, no new year."

Personally, she said hearing of the releases was "on the same level" as having babies and getting married.

Refugee Action Coalition's Ian Rintoul told AAP he understood 45 refugees and asylum seekers were being released in Melbourne on Wednesday, including a number from MITA.

He described it as the biggest development in the story of offshore processing since the Kids Off Nauru campaign in 2018 and "quite a breakthrough".

Greens senator Nick McKim, who has visited some of the men in Melbourne, told AAP he was ecstatic.

"Just to think that these guys, no matter whether they're from Manus or Nauru ... they've been brutalised and imprisoned for well over seven years now and to think they'll be breathing free air for the first time, it's quite emotional."

McKim called for the remaining detainees to be released with support, permanent protection visas and the pathway to citizenship.

The medevac law, repealed in December 2019, allowed independent doctors to recommend the transfer of people held in Nauru and Papua New Guinea to Australia for medical purposes.

Many have been held in detention since arrival, while refugees transferred under other provisions have been released.

Meanwhile, 18 refugees were flown from Nauru to Australia on Monday and are quarantining for 14 days at Sydney's Villawood detention centre, detainees and advocates said.

The number of refugees still held offshore is now below 270.

The Department of Home Affairs told AAP in a statement: "The Australian Government's policy is clear that no one who attempts illegal maritime travel to Australia will be permanently settled here."

It said people held in the hotels were only brought to Australia temporarily for medical treatment and should finalise their medical treatment and go to the United States, Nauru or PNG, or their home country.

The government has not returned anybody to offshore detention in years, despite some refugees' requests.

A number have been rejected from resettlement in the United States and are unable able to return to their home countries.

Australian Associated Press