The announcement comes as rights groups voiced concern that 200 Sri Lankans may have been handed over, including Tamils who say they face persecution at home.

BBC News reported that the Australian government has not commented on other possible cases, but has confirmed that the asylum seekers were subject to ‘enhanced screening’ to ensure compliance with Australia’s international obligations.

The asylum seekers, including four Tamils, were transferred at sea just outside the Sri Lankan port of Batticaloa. This is the first time the government has confirmed it has intercepted people at sea, screened them and returned them to their country of origin.

Immigration Minister Scott Morrison said only one person may have had a case for asylum but he opted to return voluntarily with the rest of the passengers.

Australian shadow minister for immigration Richard Marles had ‘deep concerns’ about how the processing system could have been performed by video link.

“We have grave concerns about how it is possible to assess people’s asylum claims while they are at sea,” he said.

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