Australian authorities used the cover of darkness to whisk a group of Vietnamese asylum seekers back to their homeland by plane, where three of them have been detained, a Vietnamese advocacy group says.

Prime Minister Tony Abbott on Monday refused to comment on the reports, and instead questioned the strength of Labor's commitment to turning back asylum seeker boats after it adopted the policy at the weekend.

Prime Minister Tony Abbott refused to comment on reports the Vietnamese asylum seekers had been returned, saying it wasn't his government's job to "run a shipping news service for people smugglers". Credit:Andrew Meares

It comes as Labor signalled that should the party be elected, asylum seekers would be returned to the country they were fleeing, rather than a transit nation, if their refugee claims were rejected.

There are reports that the group of Vietnamese asylum seekers, which is thought to include two babies, arrived back in Vietnam on Sunday. Australian authorities are believed to have intercepted the group's boat off the coast of Dampier in Western Australia last week.