The boat was detected off the southern coast of Hambantota on Thursday and brought ashore for investigations, the navy said in a statement.

Boats from Sri Lanka take up to three weeks to reach Australia, although some migrants travel by air to Indonesia and then take wooden boats to the Australian coast.

People smugglers charge up to $5,000 for a one-way journey to Canada, Europe, Australia or New Zealand, but Sri Lanka's navy has stepped up patrols in recent times to stop illegal immigrants leaving the island's shores.