The decision to increase the alert level on Friday followed a spike in "chatter" detected in a sixfold increase in counter-terrorism operations during the past year.

Mr Abbott on Saturday repeated his assurance that the upgraded alert level did not mean a terror attack was imminent.

But it was designed to raise community awareness about the increased likelihood of a terrorist attack in Australia, with people urged to contact the authorities if they noticed anything suspicious.

"People should go about their lives normally, reassured that strong arrangements are in place to detect, to prevent and to respond to terrorism," Mr Abbott said in a statement on Saturday.

"The government is ... taking considered action so that you can continue to lead your lives confident that everything, everything possible is being done to protect you."

NRL and AFL finals in Perth, Townsville and Sydney are expected to undergo new security measures on Saturday. They are the second lot to be played under the high threat rating after two games in Melbourne and Sydney on Friday night.

Security will also be increased at airports, ports, military bases, government buildings and large public events.

NSW police intend focusing their efforts on popular landmarks such as the Sydney Harbour Bridge, and "soft targets" such as shopping centres.

Mr Abbott said the nation's security agencies always worked "quietly and purposefully" behind the scenes, and steps were being taken to make it harder for would-be terrorists to depart from Australia.

It's believed between 50 and 60 Australians are fighting with Islamic extremist groups in the Middle East, including the Islamic State of Iraq and the Levant and Jabhat al-Nusra.

Labor's Parliamentary Secretary has broken her party's stance of bipartisan support for raising the terror alert, branding Prime Minister Tony Abbott a "terror" and criticising the Coalition's domestic policies.

The West Australian MP Alannah MacTiernan took to Twitter late on Friday night tweeting: "The Jihadi threat is real but many Australians also see Abbott as a terror as he takes a wrecking ball to our social infrastructure".

Using the terror alert as an opportunity to attack Mr Abbott's domestic policies contradicts the position of Opposition Leader Bill Shorten who, on Friday afternoon, vowed his full support to the Prime Minister on the matter of national security.

"The Prime Minister and I are partners when it comes to matters of national security and protecting Australians. We are in this together," Mr Shorten said.

"This is not a distant crisis for us. It is absolutely in our national interest that ISIL be defeated. I thank the Prime Minister for his willingness to engage with the opposition."

Mr Shorten said he had been personally briefed by Mr Abbott this week.

"When it comes to fighting terrorism we're most certainly all in this together," he said.

Yet despite the Labor leader's public support of the Abbott government on national security, Ms MacTiernan is the third Labor member to link the threat of the terrorist group Islamic State with Mr Abbott's domestic policies, saying it is a distraction from the budget.

Two weeks ago Labor senator Sue Lines also accused the Prime Minister of "scaremongering" over national security and using the situation in Iraq as a "shield" to deflect from its budget mess and to improve his position in the polls.

Ms Lines said the government's "Team Australia" rhetoric is "threatening" because it tells groups within the community they are either "in or out".

"[The Prime Minister] is just using this as a shield to try and deflect from the awful mess they're in with their budget," she told Fairfax Media.

Last month, outspoken senator Kim Carr also reportedly said: "This government is seeking to get away from discussion about real budgetary problems".

Queensland Liberal MP Wyatt Roy told Fairfax Media that the Abbott government took any threats to national security seriously.

"I would hope the Opposition Leader would ensure that his Parliamentary Secretary is acting in the national interest," he said.

"The Coalition takes these matters serious and would always act in the interest of national security."

smh.com.au, with Latika Bourke