Asylum seekers at the Manus Island detention centre say they are prepared to die and donate their organs to Australians, with one detainee adding the move would mean at least part of them would taste freedom.

The message came in the form of a letter written by an asylum seeker at the Australian-run facility in Papua New Guinea and obtained by the ABC.

"All asylum seekers on Manus Island in hunger strike ask you to hand over our medical records to organ donation organisation in case of our fatalities inside the cage," said the letter, addressed to service providers Transfield and International Health and Medical Service.

"This way at least a part of us may one day feel sweet taste of FREEDOM."

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Protests at the facility are entering their seventh day, with the detainees of at least one compound locking staff out and protest actions continuing in other compounds.

"We are in our hunger strike and if someone dies, we hope that you, we already give up our organs to Australian people to show like, we are honest people; we are loyal people; we don't mean any trouble; just what we all need, a good life and a peace life," one asylum seeker said.

The ABC has received several reports that PNG police mobile squad units will be deployed today to break up the protests.

The reports cannot be independently verified.

An asylum seeker said the police "SWAT teams" were known for their brutality.

"They said, maybe some team — they're called SWAT team — will arrive tomorrow. And if anyone did trouble, we will uptake in every compound," the male asylum seeker said.

"They are waiting for people in Delta to feel weak, because now in Delta 24 hours no water, no food, nothing.

"In Delta and Oscar if the SWAT team come in, they will beat the people very hard. And I know many people, they said 'we will not give up' and I think some people will die.

"Because already the boys, they make the rope and they all ready to hang themselves. And I heard someone in the compound, they said, 'we are ready, if they come in, we want to poison ourselves'."

Protesters against PNG resettlement

Photographs and footage have been sent to the media by asylum seekers, showing men who had reportedly fainted after days of hunger striking being carried away on stretchers.

In one video, a man is lifted into what appears to be a dormitory at the centre.

On the back of the door graffiti reads: "The Aussie Nigga."

A message written on a door at the detention centre. ( Supplied )

The asylum seeker who sent the footage said he did not know which compound it was from or what it meant.

Racial slurs against Papua New Guineans were a factor in the riots that claimed the life of Reza Barati almost a year ago.

Separate photographs of graffiti written on doors read "Help us!!" and "Where is the humanity?" and "They killed our soul!!!".

Banners hung at the centre asked for assistance from the United Nations and Red Cross.

The asylum seekers are protesting about the prospect of refugees being resettled in PNG.

Claims drinking water cut to detainees

Refugee advocates have said Manus Island detention centre managers have cut off the supply of drinking water.

The Refugee Action Coalition's Ian Rintoul said removing drinking water could have fatal consequences.

"Depriving people of water ... might be associated with some kind of atrocious dictatorship, but [depriving] drinking water from people who are in a tremendously hot environment — it beggars belief that we have got a management on the island that would consider sinking to those kinds of depths," Mr Rintoul said.

Asylum seekers said they were being denied food and water and had sent photos of men burrowing beneath a fence to reach crates of bottled water placed just outside the compound.

A sign erected by asylum seekers at the detention centre. ( Supplied )

A spokesman for Immigration and Border Protection Minister Peter Dutton said "food and water continue to be available".

"However, normal services and supplies in certain areas of the centre have been affected by the disruptive behaviour of some transferees. Normal services are ready to resume in those areas as soon as the situation allows," the spokesman said.

Asylum seekers have barricaded Delta compound and are not allowing staff to enter. The compound usually accommodates more than 200 men.

Other compounds remain open but asylum seekers are engaging in protest activities, with the situation at Oscar compound reportedly becoming volatile on Sunday evening.

An asylum seeker told the ABC two people drank mosquito repellent and another two drank detergent as part of their protest on Saturday night.

He said others were threatening suicide.

The Australian and PNG governments have said "non-compliant behaviour" would not change the outcomes for those seeking asylum, with resettlement in PNG the only option.

Foreign Minister Julie Bishop criticised those protesting at the detention centre.

"It is a volatile situation because these people clearly don't want to accept the safe haven that's being offered to them. However, this kind of behaviour will not be rewarded with a visa to Australia," Ms Bishop said.

Greens senator Sarah Hanson-Young urged asylum seekers not to harm themselves.

"The reports that I'm getting from inside the centre is that things are only getting worse," she said.

"I fear for the lives of those inside, their mental health, the distress they're feeling."