Australia has unveiled plans to increase government powers to strip citizenship from people convicted of "terrorism", and to control the movements of Australian fighters who return home from the battlefields of Syria and Iraq.

Prime Minister Scott Morrison said on Thursday that his government wanted powers to expel anyone convicted of a "terrorist" offence, even native-born Australians, as he singled out Muslim leaders as having a "special responsibility" to prevent acts of violence commited by members of the community.

"People who commit acts of terrorism have rejected absolutely everything that this country stands for," Morrison told a hastily organised press conference in Sydney.

"This is something that can't be tolerated, and for those who would engage in this sort of activity, and they have citizenship elsewhere, or we have reason to believe they do, they can go."

This comes a day after Muslim leaders in Australia boycotted a roundtable meeting called by the conservative leader, who has asked the Muslim community to do more to halt attacks in the country.

Community leaders in an open letter said they are "deeply concerned and disappointed" with statements made by the prime minister and senior officials, which "infer that the community is collectively culpable for the criminal actions of individuals and should be doing more to prevent such acts of violence".

"These statements have achieved nothing to address underlying issues, but rather, have alienated large segments of the Muslim community," they said in the letter published by Australian media.

Legislation to amend Citizenship Act 

Australia's current Citizenship Act allows authorities to revoke citizenship from people jailed for six years or more for "terrorist" activities, but only if they are already dual nationals.

Morrison called these limits "unrealistic" and said the law should be broadened to strip citizenship from convicted "terrorists" if they could "reasonably" be expected to gain citizenship in another country through their parents or grandparents.

The conservative government will submit legislation to amend the Citizenship Act to enshrine these new powers, he said, in the final two-week parliamentary session of the year that begins on Monday.

His proposals came two days after police in the country's second largest city, Melbourne, arrested three Australian-born men of Turkish descent for allegedly plotting a mass shooting in the city.

Less than two weeks earlier, a Somalia origin man went on a stabbing spree in Melbourne, killing one man and wounding two others before being fatally shot by police. 

Authorities said all four men were inspired by propaganda from the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group, even though none had any direct links to such organisations.

Legal challenges

Experts say the proposed legislation was likely to face legal challenges. 

"It is not clear that the commonwealth has the power to kick out people who have been here for many, many generations," said Sangeetha Pillai, constitutional lawyer at the Kaldor Centre, University of New South.

"This legislation would make some people stateless at least temporary and in some cases, permanently."

Morrison, the prime minister, said the law will also seek the power to impose "temporary exclusion orders" on so-called "returned foreign fighters" - Australian citizens who travel to conflict zones to fight alongside armed groups.    

Modelled on a British law, the provision would allow Australia to bar the return of a citizen for up to two years, and to impose strict conditions on their activities once they come home.

Home Affairs Minister Peter Dutton said there had been seven "terror-related" attacks in Australia while authorities had thwarted 15 other plots since 2014.

Nine people convicted of "terrorism" have already had their citizenship revoked under existing law, mainly for activities overseas, he added. 

"We assess there are around 50 Australian dual citizens who may be eligible to lose citizenship under the current provisions, and even more with the changes we are announcing today," Dutton said.

Morrison and Dutton also said they would renew a push for controversial legislation which would allow authorities to break into encrypted messaging apps that police say are widely used by extremists and other criminals.

The law, which would force app developers and telecom companies to provide police with the ability to decrypt messages, has drawn strong criticism from civil liberties groups.

Morrison heads a minority coalition government that must call a national election before May 2019 but is trailing well behind the main opposition Labor Party in opinion polls.

As campaigning builds towards the election, Morrison and Dutton have led a tough law-and-order push around "terrorism" and immigration.