Australia's hardline policy on asylum-seekers, who have been pushed back by the boatload and incarcerated in offshore camps, is under pressure as public sympathy for Syrians escaping conflict swells in a nation built on migration.

While Europe opens its doors, at least temporarily, in the face of its worst refugee crisis since World War II, Prime Minister Tony Abbott has successfully closed Australia's borders to refugee boats, with no arrivals in more than a year.

From a handful that made it in 2008, boatloads of people from war-torn Afghanistan, Sri Lanka and the Middle East were coming almost daily by 2013, with hundreds of people drowning in the treacherous northern waters.

Refugees still come to Australia, via an orderly resettlement programme. But turning back the boats, strict secrecy about operations on the high seas, and banishing asylum-seekers who do make it to two remote Pacific islands are the hallmarks of the policy that ended the crisis.

Although the policy stopped the drownings, human rights organisations have slammed the prolonged detention of asylum-seekers, including children, in wretched camps as cruel and in breach of Australia's legal obligations.

The controversy, including reports of suicide and child molestation in the centres, has played out far from the public eye. But the image of a drowned Syrian toddler that moved Europeans has also shifted the debate in Australia.

'OPEN THE DOORS'

Thousands gathered across the country Monday for "Light the Dark" rallies in memory of Aylan Kurdi, calling for more refugees to be welcomed into a country that over the decades has ushered in waves of migrants and created a vibrant multicultural society.

Abbott admitted in parliament that "all of us were moved to tears by that poignant image of the drowned child" and said that Australia would "play our part".

"It is the government's firm intention to take a significant number of people from Syria this year," he said, without specifying how many.

There will be no budging on the policy of "pushing back" the boats, but one option may be an emergency intake similar to the evacuation of Kosovo refugees in 1999.

Australia could also lift its current annual humanitarian refugee intake from 13,500 people, with aid agencies urging this be raised to 30,000 places in response to the global crisis.

Pamela Curr from the Asylum Seeker Resource Centre told the rally in Melbourne that advocates would continue to raise the issue "until our government opens its heart, opens its mind and opens the doors of Australia".

Even within Abbott's conservative Liberal Party, which has been in lockstep behind the asylum-seeker policy, there are now calls for a greater humanitarian response, with one lawmaker calling for up to 50,000 Syrian refugees to be accepted.

Mike Baird, the premier of Australia's most populous state, New South Wales, acknowledged Saturday that "stopping the boats can't be where this ends".

"We cannot see the images we have seen, and feel the things we have felt, and then go back to business as usual," he said in comments that represent a new tone in the debate.

NO END TO 'PUSHBACK'

Despite the outpouring of sympathy, there is no indication that Australia will dismantle the policies for "stopping the boats", with Immigration Minister Peter Dutton last week defending them as crucial to preventing more disasters at sea.

"Our policies are lawful. They are safe. And they work. They save lives," he said.

But critics say the policy of turning back boats and the offshore detention of asylum-seekers, while effective in preventing flows to Australia, simply shifts the problem elsewhere.

Refugee law expert Michelle Foster from the University of Melbourne said that asylum-seekers coming to Australia on unauthorised vessels were overwhelmingly found to be genuine refugees.

"If a government chooses to turn back boats it does nothing to solve the global refugee problem... you are simply requiring them to seek protection elsewhere," she said.

Sarah Joseph, director of the Castan Centre for Human Rights Law at Monash University, said that while the government has applauded its policies as effective - "whether we've actually saved lives... that's actually impossible to know".

She noted that the detention centres on the Pacific islands of Nauru and Papua New Guinea's Manus island, where some 1,500 people are held, are by all accounts "appalling places for people to actually live".

Joseph said Australia's method of regulating flows of asylum-seekers could never be applied to Europe, which is much closer to the conflict zones and faces an unmanageable number of people and boats.

"And where are you going to send them back to? Are you telling people, 'Look, don't worry, just stay in Syria?'"