Behrouz Boochani was taken away during a police raid on the camp on PNG's Manus Island, according to rights groups and pictures posted by other detainees on social media.
Detainees said the police destroyed property and began forcing some of the around 400 refugees at the camp into buses to be transported to other transition centres on the island.
"We have confirmed that he has been taken away," Shen Narayanasamy of Australian activist group GetUp told AFP, speaking of Boochani.
"We are very concerned about his welfare... He's become a voice on behalf of the men detained in this camp now for four years," she said.
Also Read
"The police station and the jail inside Manus are places in which it's very difficult to get information."
Boochani had been regularly tweeting and talking to journalists by phone about the conditions in the camp.
Narayanasamy said his phone had been taken away from him, and other refugees were worried police now had a policy of arresting people who had spoken to media outlets.
Boochani gained international recognition for shooting footage on a smartphone inside the Manus camp for a film that was shown at the London Film Festival in October.
Global rights group Amnesty International called for his immediate release, saying that it "seems this is a deliberate attempt to isolate human rights activists from the wider group".
The refugees are barred from resettling in Australia, but Canberra has struggled to move them to third-countries including the United States.
Disclaimer: No Business Standard Journalist was involved in creation of this content