SYDNEY (AP) -- Australia's government promised Tuesday not to hand over a group of asylum seekers to the Sri Lankan government without three days' notice amid a court challenge and uproar from human rights groups.

The government's pledge came during a High Court hearing held one day after Australia's immigration minister confirmed that another boatload of asylum seekers had been intercepted by Australian border patrol and handed to Sri Lankan authorities in a transfer at sea last month. Refugee advocates and human rights agencies argued that the asylum seekers could face persecution in their home country.

Lawyers representing some of the Sri Lankan asylum seekers on the latest intercepted boat went to the High Court to stop the 153 people on board from also being returned to their home country. They are currently being held on an Australian customs vessel.

High Court Justice Susan Crennan, who issued a temporary injunction late Monday night halting any further transfers, adjourned the matter until a later date following Tuesday's hearing. In the meantime, the government's lawyer, Justin Gleeson, said no asylum seekers would be transferred without 72 hours' written notice.

The issue erupted Monday after Immigration Minister Scott Morrison confirmed that Australian border patrol had intercepted a boat carrying 41 Sri Lankans off the Cocos Islands in the Indian Ocean in late June and handed them over to the Sri Lankan government on Sunday.

Tuesday's court hearing marked the first time the government acknowledged the second boat's existence, and Morrison still has yet to comment on where or when that boat was intercepted.

The hearing has no impact on the 41 Sri Lankans who have already been returned to Sri Lanka.

A Sri Lankan court on Tuesday detained five alleged people smugglers who were among the 41 aboard the boat. Twenty-seven other adults were accused of illegally leaving the country and were released on bail, while nine children who were aboard the boat were discharged.

Ruwan Rangana, 29, said he paid 150,000 rupees ($1,150) to smugglers for the seven-day journey to Australia. "I went there seeking a job,'' he said.

The attorneys representing some of the asylum seekers on the latest boat argue that their clients could face persecution in Sri Lanka, which emerged in 2009 from a brutal civil war between government troops and the now-defeated separatist Tamil Tiger rebels. Refugee advocates say ethnic Tamils still face violence at the hands of the military.

The temporary reprieve granted Tuesday was trumpeted as a win by one of the asylum seekers' lawyers, George Newhouse, who said "a group of vulnerable men, women and children will not be sent back to their persecutors in Sri Lanka.''

Facing a surge of asylum seekers trying to reach Australian shores, the nation's conservative government implemented a tough policy of turning back their boats. Until now, the vessels have been returned to Indonesia, where asylum seekers from across the world pay people smugglers to ferry them to Australia aboard rickety boats prone to sinking. Monday marked the first time the government confirmed it had screened asylum seekers at sea and returned them directly to their home country.

The seemingly quick process by which Australia rejected the refugee claims is also facing scrutiny. Rather than bringing the asylum seekers to Australia's processing centers on the Pacific island nations of Nauru and Papua New Guinea, the claims were assessed on board an Australian vessel.

The United Nations refugee agency, UNHCR, issued a statement Tuesday saying it was "deeply concerned'' by the decision to hand the asylum seekers back to Sri Lanka, and about the fate of those aboard the second boat.

The agency questioned the at-sea assessment process, saying that without further details from the government it cannot say whether Australia is violating its international obligations to refugees.

"UNHCR's experience over the years with shipboard processing has generally not been positive,'' it said in a statement. "Such an environment would rarely afford an appropriate venue for a fair procedure.''

Gleeson, the government's lawyer, said the asylum seekers were intercepted outside Australia's territorial waters and therefore not subject to any obligations under the nation's Migration Act, which sets guidelines on how asylum seekers are processed.

Prime Minister Tony Abbott said the government's tough asylum seeker policies were, in fact, an act of compassion.

"As long as the boats keep coming, we will keep having deaths at sea,'' Abbott told Australia's Channel 7. "So the most decent, humane and compassionate thing you can do is to stop the boats.''