Australia has raised its terrorism threat level from medium to high, Prime Minister Tony Abbott has announced.
The move comes in response to growing concern over the domestic impact of militant conflicts in Iraq and Syria.
Security officials were concerned by the growing number of Australians “working with, connected to or inspired by” extremist militant groups, the BBC quoted Abbott as saying.
But he said that there was no specific intelligence regarding a planned attack.
“I want to stress that this does not mean that a terror attack is imminent. We have no specific intelligence of particular plots,” he told a press conference.
“What we do have is intelligence that there are people with the intent and capability to mount attacks here in Australia.”
Officials say dozens of Australians have gone to fight for extremist militant groups such as Islamic State and Jabhat al-Nusra (also known as the al-Nusra Front) in the Middle East.
They are worried about the impact of both returning fighters and supporters of these groups on domestic security.
It is the first time Australia has moved from medium to high - the second-highest rank - since the threat level system was introduced in 2003.
“Medium” means an attack could occur. It is followed by “high”, which means an attack is likely and then extreme, meaning an attack is imminent or has occurred.
Abbott said that while the move would not make a great difference to daily life, people could notice more security at airports, ports, military bases, government buildings and large public events.
Officials say at least 60 Australians are believed to be fighting with jihadist groups in Syria and northern Iraq, and 15 Australians have been killed so far in these conflicts, including two suicide bombers.
About 100 more Australians are thought to be actively supporting these groups, they say.
CIA Triples IS Member Estimate
The CIA says the Islamic State (IS) militant group may have up to 31,000 members fighting in Iraq and Syria - three times as many as previously feared.
A spokesman said the new estimate was based on a review of intelligence reports from May to August.
The CIA had previously believed that IS had about 10,000 fighters, spokesman Ryan Trapani said.
“This new total reflects an increase in members because of stronger recruitment since June following battlefield successes and the declaration of a caliphate, greater battlefield activity, and additional intelligence,” he added.
More than 15,000 foreign fighters from more than 80 countries have gone to Syria, a CIA source told CNN on Thursday. 2,000 of those are believed to be Westerners.
The revision comes a day after US President Obama outlined a plan to “degrade and destroy” IS and to increase military support for allied forces engaged in fighting the group.
For the first time, he authorized air strikes against the group in Syria.
The US has already carried out more than 150 air strikes against IS in Iraq, but has ruled out sending ground troops.
