Australia's official terror alert level has been raised to "probable" amid heightened community tensions over the war in Gaza.

Security authorities believe the chances of a violent extremist act are now more likely than when authorities lowered the alert level to "possible" in November 2022.

ASIO's director-general Mike Burgess said Australia's security environment had become more volatile and unpredictable.

"More Australians are being radicalised and being radicalised more quickly," Mr Burgess said.

"More Australians are willing to use violence to advance their cause. Politically motivated violence now joins espionage and foreign interference as our principal security concerns."

He also noted the conflict in Gaza was not the "cause" for raising the terror level, though it had been a "significant driver".

Mr Burgess said, however, raising the threat level did not mean ASIO had intelligence about plans of a current attack or expectations of an imminent attack.

But he said agencies had disrupted eight incidents in just the last four months that involved alleged terrorism or were investigated as potential acts of terrorism.

Those cases included risks of knife attacks or attacks with improvised weapons and involved young people who had been radicalised — the youngest 14, and the oldest 21.

PM says Australians must 'lower temperature' of debate

Prime Minister Anthony Albanese said the raised level had been driven by increases in youth radicalisation, online radicalisation and the rise of "new mixed ideologies".

"I want to reassure Australians probable does not mean inevitable, and it does not mean it is intelligence about an imminent threat or danger," Mr Albanese said.

"[But] when the temperature of the security environment is rising, we must lower the temperature of debate."

Opposition Leader Peter Dutton called on Australians to watch out for terror threats.

"We do live in a precarious time," he said.

Mr Albanese said Australians must be able to resolve their differences peacefully and debate political issues like the conflict in Gaza peacefully.

"No one is suggesting people should have conformity to particular views, but the way people express things is important," he said.

"It is not normal to have people in occupations for months outside electorate offices, where the work of those electorate offices is to assist people."

Asked if he agreed if the temperature should be brought down, Mr Dutton said he did.

But the opposition leader reiterated his criticism of Mr Albanese's response to pro-Palestinian protests outside the Sydney Opera House last October and the ongoing encampments on University campuses.

"I think the proper response is required from the leader of our country to show strength, not weakness, and the amount of anti-Semitism that … occurring on a common basis in our country in an unprecedented way," he said.

Mr Dutton said leaders should be clear that we "adhere to a strong set of values … the rule of law" and "respectful debate".

The official terror alert level was last raised to "probable" in 2014 with the emergence of the Islamic State terrorist group.