A spokeswoman for the Australian Maritime Safety Authority said it was not clear how many people had survived.

''A people smuggler boat may have sunk in or near the south of the Sunda Strait about 3am [AEST] on Friday,'' the spokeswoman said. ''Some passengers may have been rescued by a fishing vessel.''

Australian authorities had no more details on Friday afternoon.

It's understood the incident happened within Indonesia's search and rescue zone.

More to come