Australia's terrorist alert level has been raised to high, meaning the risk of an attack is likely.
Prime Minister Tony Abbott announced the increased threat level at a press conference in Melbourne.
It takes the level from medium, when an attack "could" happen, but stops short of the highest warning level of extreme, when an attack is "imminent".
Mr Abbott says the Government has "no specific intelligence" of a plot to mount a terrorist attack.
"What we do have is intelligence that there are people with the intent and the capability to mount attacks," he said.
The move is likely to trigger increased security and a bigger police presence at upcoming football finals and other large public events.
On Tuesday, ASIO's Director-General David Irvine said he was actively considering raising the alert from "medium" to "high" because of the involvement of Australians in the Middle East war zone.
Victoria's police chief has also said he has "legitimate concerns" about an increased risk of attack.
Late last month the United Kingdom raised its alert from "substantial" to "severe", meaning that the threat of an attack was rated "highly likely".
It is the first time Australia's alert level has moved up from medium in more than a decade.
In 2002, the Government issued a general warning of a credible threat to mainland Australia by Al Qaeda.
