Representatives of the Vietnamese community in Australia fear for the safety of asylum seekers who have reportedly been returned to Vietnam.
An asylum-seeker boat was spotted off Western Australia's north coast last week, near Dampier but the federal government has declined to confirm whether the passengers have been sent back.
"I have a great fear for their safety," Victorian president of the Vietnamese community, Bon Nguyen told ABC Radio.
Australian Greens senator Sarah Hanson-Young demanded the government explain what happened to the people.
"Handing these people directly over to the Vietnamese government constitutes refoulement, which is a breach of the refugee convention," she said in a statement.
There had been an increase in people fleeing Vietnam over religious persecution, particularly Christian minorities, she said.