The Australian government must urgently intervene to halt the forced deportation of Australia's detainees on Manus Island.

"Under the cover of darkness, at least one person seeking asylum has been forcibly removed from Manus Island," Greens Immigration spokesperson Senator Nick McKim said.

"With the illegal detention centre being forced to close and the uncertainty around the US 'deal', this seems to be Peter Dutton's only 'solution' to the humanitarian crisis he has overseen."