The government is being urged to explain what is happening to sick, young children believed to be detained on border patrol boats.
The federal government has refused to confirm reports that a boat carrying 153 Tamil asylum seekers, including 30 children, is in high seas off Christmas Island.
Nor has it confirmed reports that a second boat, from Indonesia with 50 people aboard, has been intercepted by Australian Customs vessel Triton near the island.
But the Australian Greens say Christmas Islanders have said local boats are transporting supplies to Australian vessels Ocean Protector and Triton.
Greens immigration spokeswoman Sarah Hanson-Young is concerned about asylum seekers who may be on board Australian ships.
“The reports we had [were that] on board one of the boats yesterday there were children very sick after spending two weeks out on the seas,” she said in Canberra on Sunday.
Immigration Minister Scott Morrison must explain how they are treating the people who have already spent over two weeks at sea, she said.
“It seems as though it is more like `operation prison ships’ than it is Operation Sovereign Borders.”
There is speculation the federal government may find it difficult to turn back either boat as Indonesia heads for an election.
Meanwhile, Labor MP Alannah MacTiernan says she saw an “enormous amount” of maritime activity on her visit to Christmas island on Friday.
She was later informed two boats were offshore.
“They had gone out and intercepted people and they had loaded up people on the navy or border protection vessels, and brought [them] back onto Christmas Island waters,” Ms MacTiernan told AAP on Sunday.
Detention centre staff were preparing for arrivals as they waited for official notification.
“They hadn’t had final instructions that the people would be coming to Christmas Island,” Ms MacTiernan said.
Any landing would be the first in six months.
Mr Morrison said on Saturday there were no significant incidents to report.
But Labor immigration spokesman Richard Marles accused Mr Morrison of going into hiding on the matter.
“Day after day he proclaimed his political scoreboard by beating his chest on the good days,” Mr Marles told Sky News on Sunday.
“Now he goes out and trumpets secrecy. It simply isn’t good enough.”
Mr Morrison’s office told AAP the minister had nothing to add to comments he gave in a press conference on Saturday, during which he refused to say if there were any boats.