Tamil asylum seekers believed to have been intercepted on astricken fishing vessel off Christmas Island might be forcibly returned directly to south Asia by the Australian government.

Immigration Minister Scott Morrison said on Monday night the government was prepared to talk with any country to enforce its policy of stopping boats from reaching Australia.

If the asylum seekers are in Australian custody, they are being held without communications. The last contact made by satellite phone was at the weekend.

Removing the asylum seekers from Australian territory would be illegal under international law.

It’s understood the 153 Tamil asylum seekers, all originally from Sri Lanka, left Pondicherry in southern India on a fishing trawler 17 days ago.

The last report from the vessel said it was running low on oil about 175 nautical miles off Christmas Island.

Mr Morrison’s office on Monday refused to confirm the existence of the boat, nor would it confirm any action taken by the Australian customs vessel Ocean Protector, last seen off the coast of Christmas Island on Sunday near where the refugee boat is believed to have been.

Mr Morrison said Australia was prepared to work with any country to enforce Operation Sovereign Borders.

“Without specifically talking about any single country, we would engage with any other countries that we would need to engage in relation to our operations. That has been our practice until now and that will certainly be our practice going forward,” Mr Morrison said.

‘‘Public curiosity is not the same as the public interest and the public interest here that I have to assess is what is in the national interest and what is in the national interest is that we maintain the integrity of an operation that is saving lives at sea and protecting the integrity of our borders.’’

On Tuesday, Prime Minister Tony Abbott refused to answer questions about the possible return of the Tamil asylum seekers to Sri Lanka. only repeating that the government was ''stopping the boats''.

''I’m not going to comment on the operational details of what happens on the water but obviously we have been successful up till now,'' he told ABC radio.

''It’s more than six months since [a] successful people smuggling venture made it to Australia. That’s a record that the government is determined to maintain if we possibly can.''

The Indian government maintains no boat ever left its shores.

Sri Lanka’s high commissioner, Thisara Samarasinghe, said his government stood “ready to work with Australia to combat the crime of human smuggling and stop people dying at sea”.

Amid government silence, the location of the asylum seeker boat, and the welfare of those on board, is a mystery. It has been speculated Australia might be arranging to transfer the asylum seekers to a Sri Lankan navy vessel for return to that country.

Ian Rintoul, of the Refugee Action Coalition, said it had become apparent that Australia had intercepted the asylum seekers.

“It has been 48 hours and under Scott Morrison’s own rules he would have had to announce there had been an incident at sea by now, so you can assume they have been taken off their boat.”

“There is a lot of speculation that they will rendezvous with Sri Lankan navy boats and hand them back.”

Four Sri Lankan navy officers and sailors have been arrested and charged with involvement in people-trafficking, including alleged smuggling kingpin, Lieutenant Commander Sanjeewa Annatugoda, who briefed Australian officials on naval operations.

The 1951 Refugee Convention, to which Australia is a party, defines a refugee as a person outside the country of his or her nationality “owing to well-founded fear of being persecuted” and says that “contracting states shall not expel a refugee lawfully in their territory save on grounds of national security or public order”.

The convention principle of “non-refoulement” prohibits sending people back to their home countries if they could face persecution.

Australian National University professor of international law Donald Rothwell said there would be ‘‘very direct questions raised’’ if Australia was sending people back to the country of origin they had fled.

“Returning people on boats to Indonesia is a separate issue because Indonesia is a transit point,” he said.

“But if people are being returned to their place of nationality or homeland and that is the place they are seeking to flee because they have a well-founded fear of persecution, then that raises a direct issue as to whether or not Australia would be in conflict with its international refugee obligations.”

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