A refugee, who had resettled on Nauru, has drowned along with a second person who was attempting to rescue them.

A spokeswoman for Immigration Minister Scott Morrison says the person was processed at Australia's Immigration Detention Centre and had been granted a refugee visa by the Nauruan government.

The spokeswoman says it appears the death was accidental but authorities on Nauru are investigating.

"We understand from initial reports that the first deceased person was a private resident of Nauru, on a Nauruan refugee visa, and was accidentally drowned," the Minister said in a statement.

"This is a matter for the government of Nauru as it pertains to an incident involving a resident and citizens of their own country that occurred within their jurisdiction," he said.

The person was not a resident at the offshore processing centre and was originally from Pakistan.

Mr Morrison extended his sympathies to the families and friends of both people who drowned.

"It is a very sad incident. This person I understand was a Pakistani national originally. They had been found to be a refugee and they had been resettled. So they were a private resident on Nauru just like someone who'd be on a visa in Australia," Mr Morrison said.

It is understood the second person who died was a Nauruan citizen.

A third person was also injured.

The Nauruan government labelled the deaths a 'tragic drowning accident' and asked that it not be used to gain political mileage.

"We are devastated that we have lost a new member of our community, and applaud the bravery of those who attempted the rescue," it said in a statement.

"We mourn the loss of one of those rescuers and our thoughts are with the second, who remains in a serious condition.

"While the circumstances of the tragedy are under investigation, sadly - like in any coastal community - accidents in the water can happen."