The Australian government's travel advice for Britain has changed after British Prime Minister Theresa May upgraded the terrorism threat from "severe" to "critical", meaning another attack may be imminent.
The Department of Foreign Affairs and Trade now urges a "high degree of caution" for anyone visiting Britain.
Also, Foreign Affairs Minister Julie Bishop has advised Australians not to travel to Manchester for the time being.
Ms Bishop also said there was still no suggestion that any Australians were caught up in the Manchester bombing, which has claimed 22 lives.
After a meeting of the Australian government's high-level National Security Committee on Tuesday night, the domestic threat level will remain at "probable", where it has been since late 2014.
"We would recommend that anyone seeking to travel to the United Kingdom read our travel advice, which is under constant review and brings the latest information that we have to the Australian public," Ms Bishop told Nine's Today show.
"Obviously with the threat assessment being raised that will change our assessment of travel to the United Kingdom."
British authorities are investigating whether the suicide bomber, named as 22-year-old Salman Abedi, was working alone or as part of a network.
A 23-year-old man, believed to be the alleged attacker's brother, has been arrested.
Mrs May has announced that the country's armed forces will be deployed to work with police to help secure key sites and other public events.
Following discussions with the Australian high commissioner to Britain, Alexander Downer, and the British authorities, Ms Bishop said there was still no evidence any Australians were involved.
"But I must point out that the grisly task of identifying bodies continues and we are in touch with all the major hospitals in Manchester," she said.
Australian Prime Minister Malcolm Turnbull said security arrangements, including for mass public gatherings, were constantly being reviewed and upgraded by federal and state authorities.
"It is vitally important that we destroy the terrorists in the Middle East, destroy the so-called caliphate, which they [the Islamic State group] have used as such a big recruiting tool both drawing people into the Middle East and, of course, recruiting adherents outside," Mr Turnbull told ABC radio.
"We have to do that and we also need to be constantly vigilant and improving our intelligence services and our hard security protections here at home."
The Prime Minister noted increased police presences at crowded events and the introduction of more obstacles, such as bollards and barriers, to hinder attacks with vehicles.
According to the government, 63 people in Australia have been arrested on terrorism-related charges and 12 terrorist plots have been foiled since September 2014.
