Indonesia’s foreign minister says the apparent addition of three extra passengers to an asylum seeker boat turned back into Indonesian waters is a “very serious development”.

The asylum boat’s crew reportedly told Indonesian navy investigators that two Australian warships put three extra people on board their boat – an Indonesian and two Albanians – before they were escorted back to Indonesian waters on Sunday.

Speaking at a leader’s summit in Bali, foreign minister Marty Natalegawa said the information that people were put on the boat by Australian authorities was yet to be confirmed.

“I am informed that apart from the apparently original 18 asylum seekers who were in the original two boats, apparently some additional three individuals were added to the boat that was forced back to Indonesia,” he said.

“So this is – if confirmed – obviously this is a very serious development.

“As I said from the beginning we are risking a slippery slope in the facilitation of Australia’s government for these individuals to be forced back to Indonesia.”

Indonesia’s navy has issued a statement based on testimony given by the crew, who were found on a wooden boat stranded on a small island in eastern Indonesia.

The crew members say they were in Australian waters on May 1 while taking 18 asylum seekers from India and Nepal towards Ashmore Reef.

According to the crew, the Australian ships escorted them back to Indonesian territory a day later.

Obviously this is a very serious development.

Indonesian navy spokesman Colonel Suradi Agung Slamet says the crew told investigators the extra passengers were put on the boat at 3:00am on Sunday and the boat re-entered Indonesian waters at 5:30am.

By 8:00am the boat’s engine had died and it was stranded on Lay Island where it was checked by the Indonesian navy, crew members say.

In response to the claims, a spokeswoman for Immigration Minister Scott Morrison says the Government does not comment on “on-water operations”.

Greens leader Christine Milne says she is shocked by the reports.

She says if they are true, it would be in complete contravention of international law.

“These are really serious breaches of not only international law but of appropriate process,” she said.

Abbott cancelled trip to Bali summit

Last week, Prime Minister Tony Abbott cancelled a trip to the Bali summit, which was to have included his first meeting with his Indonesian counterpart since relations soured last year over spying revelations.

The ABC understands Mr Abbott pulled out because of an asylum seeker “operation” that Australian Government sources told the ABC had the potential to cause “embarrassment” to the Indonesian government.

The Government said the visit was cancelled to allow Mr Abbott to concentrate on next week’s federal budget.

Mr Natalagawa says Indonesia has not received a “detailed explanation” for the Prime Minister’s absence.

“I wouldn’t want to enter into speculation about the rationale behind it,” he said.

“I’m certainly not a mind reader and not in a position to be able to ascertain about exactly what it is making it impossible for the Prime Minister to be in Bali at this time. But it is a matter for the Australian Government to be able to share.”