The Free Filep Karma Campaign has called for Indonesia's government to meet its legal obligations to facilitate medical treatment for the high-profile Papuan prisoner.
Filep Karma, who is serving a 15-year jail term for raising the banned Papuan Morning Star flag, has been seriously ill in Jayapura's Abepura prison but officials have refused to pay for his treatment.
The UN Working Group on Arbitrary Detention recently declared Mr Karma's detention illegal under international law.
A human rights lawyer who works with the Campaign, Melinda Janki, says Indonesia must adhere to the UN's standards on the minimum treatment of prisoners.
"And the important thing to remember here is that this should not be happening. Filep's imprisonment is illegal, he shouldn't be there. He should be free. And again, that's a very grave cause for concern when you have countries illegally imprisoning people."
Melinda Janki of the Free Filep Karma Campaign