A senior Australian doctor offering medical care to refugees on Nauru was detained by police and deported from the island this afternoon.

Key points: Dr Montana was reportedly arrested after taking a photograph of a child

Dr Montana was reportedly arrested after taking a photograph of a child One source said the Nauru Government was becoming "increasingly paranoid"

One source said the Nauru Government was becoming "increasingly paranoid" Dr Montana replaced Dr Christopher Jones only last month, after he was also deported

The ABC has confirmed Dr Nicole Montana was detained by police yesterday evening.

Dr Montana works for the health contractor IHMS and was the most senior Australian health professional currently working on the island.

The ABC understands Dr Montana was detained because she took a photo of a child being treated at the regional processing centre on Nauru.

The Government of Nauru forbids doctors and other medical workers from photographing their patients in order to prevent leaks to the media and refugee advocates.

Australian Government sources say Nauruan officials probably suspected that Dr Montana was planning to leak the photo — but they maintain that was unlikely, suggesting Dr Montana was treated unfairly.

Another source said the Nauruan Government was becoming "increasingly paranoid".

In a statement, IHMS said its "Senior Medical Officer was stood down on 16 October 2018 for a breach of Regional Processing Centre rules."

"A replacement Senior Medical Officer is already in Nauru, there has been no impact on the services provided to transferees," the statement said.

The relationship between the Nauru Government and Australian medical professionals working on the island has deteriorated rapidly this year.

Only last month Dr Montana's predecessor Dr Christopher Jones was also deported from Nauru, after a disagreement over medical transfers of the refugees.

And earlier this month Medecins Sans Frontiers (MSF) workers were abruptly kicked off the island after Nauru cancelled its contract to provide mental health services to both refugees and residents.

Greens senator Nick McKim said offshore processing is "crumbling before our eyes". ( Supplied: World Vision, file photo )

In a statement issued on Friday, the Nauruan Government defended the move by saying MSF were not in the country to help Nauruans but rather were "political activists" in their referencing of the island nation as an "open air prison".

Doctors groups have also warned of a mental health crisis on Nauru and have been pressing the Government to allow children on the island to come to Australia for medical care.

In a statement a spokesperson for the Department of Home Affairs said the arrest was "a matter for the Government of Nauru and IHMS".

"A replacement Senior Medical Officer is in Nauru. There has been no impact to the continuity of care for transferees," the statement said.

Dr Montana was put on a flight this afternoon and is expected to arrive in Brisbane this evening.

The Nauru Government has been approached for comment.

Greens senator Nick McKim said offshore processing is "crumbling before our eyes".

"This is a humanitarian emergency, and Scott Morrison has lost control of his detention centres," Senator McKim said.

"This deportation confirms that there is no way for Australia's prisoners on Nauru to receive proper medical support."