There was rising concern on Sunday over the safety of 153 Tamil asylum seekers in a reportedly sinking ship off Christmas Island, after all communications were lost more than 24 hours ago.

According to the Guardian newspaper, this has led to speculation that the boat has been intercepted by Australian Navy personnel, amid reports that a second boat carrying asylum seekers was also stranded nearby.

The Labour MP Alannah MacTiernan told AAP on Sunday that she had seen an "enormous amount" of maritime activity by Christmas Island.

"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 said.

"They hadn't had final instructions that the people would be coming to Christmas Island," she added, stating that Christmas Island staff were on standby for a possible arrival of asylum seekers.

The Australian government continues to be silent on the issue however, despite growing international calls for action.

On Saturday, the Australian Immigration minister refused to confirm reports of the boat, telling reporters: "I am advised that I have no such report to provide to you today."

The Greens party spokesperson for immigration was quoted by AAP as saying on Sunday:

"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,"

"Immigration Minister Scott Morrison must explain how they are treating the people who have already spent over two weeks at sea"

"It seems as though it is more like `operation prison ships' than it is Operation Sovereign Borders."