SYDNEY — More than 600 people-smugglers have been arrested across six countries since Australia introduced its hardline border regime, a senior official said on Tuesday, with over 30 asylum-seeker boats turned back.

Immigration Minister Peter Dutton, in releasing details of the conservative government’s classified "Operation Sovereign Borders", said the controversial policy had saved lives.

"I’ve not had a death at sea on my watch," he said.

The military operation began in September 2013 and has managed to halt the flood of boat arrivals that characterised previous Labor administrations.

Before the conservatives took power and adopted a zero tolerance stance, an estimated 50,000 asylum-seekers flooded into Australia on more than 800 boats over the previous five years.

Hundreds more, many from war-torn Afghanistan, Sri Lanka and the Middle East, died at sea during the treacherous journey.

"People-smugglers are an evil scourge who are looking for innocent men, women and children to take money from them," Dutton said.

"They don’t care whether they make Australian land or go to the bottom of the ocean."

He said attempts to smuggle 2,500 people had since been stopped, with 33 boats turned back, mostly to Indonesia.

He thanked the governments of Indonesia, Sri Lanka, and Malaysia "who have helped us in not only deterring those boats and those ventures, but also their involvement in the arrests of people-smugglers involved in this evil trade".

Dutton, on the campaign trail ahead of a series of weekend by-elections, did not say which other countries had arrested people-smugglers.

Since the operation got underway, Canberra has sent any boatpeople to offshore Pacific processing camps in Papua New Guinea and Nauru and they are blocked from being resettled in Australia even if found to be genuine refugees.

They can either return home, make a life on Manus or Nauru, or go to a third country. More than 300 have since been resettled in the US under a deal struck with former president Brack Obama, although hundreds more remain in limbo.

Canberra says its policy deters people from embarking on the treacherous sea journey, but rights groups and the United Nations have slammed the wealthy nation for turning its back on vulnerable people.

There has also been fierce criticism of the camps, with reports of abuse, suicide and despondency.

Thousands of people marched across major Australian cities on Saturday calling for an end to offshore detention, but Dutton said any relaxation of the government’s stance would play into the hands of people-smugglers.

"We know that we’ve got 14,000 people in Indonesia, and that those people are ready to hop on boats right now," he said.

"So let’s be realistic about the threat that’s there." — AFP