The bombing appears to have happened in egress after the pop concert, at a time when security may have "let down their guard", said Craig Sheridan, a former police officer who runs security and risk management for major events in Australia.

"A similar attack can't be ruled out here," he said. "Great work has thwarted a lot of attacks in Australia but we just have to be on our guard all the time and take complacency out of the picture."

Victoria and NSW police said they would reassess the threat to Australia, and some stadiums have flagged extra police and security at a raft of major upcoming events.

The threat level in Australia remains at 'probable' and, despite no direct threat, Victoria's police chief Graham Ashton said they would "do an assessment following this event".

???NSW Police said they are monitoring events but don't believe there is any local link.

"As a matter of course, and as would be expected, we will look at the arrangements in place and determine whether any additional measures are required," a spokesman said.

Several large events are scheduled over the next week including State of Origin, Sydney FC vs Liverpool FC at ANZ Stadium and AFL games at the SCG, MCG and Melbourne's Etihad Stadium.

ANZ Stadium, which recently hosted concerts for pop stars Adele and Taylor Swift, said there will be a high presence of police and security for the Liverpool showcase match on Wednesday.

"The Stadium is constantly reviewing its security procedures and is having ongoing dialogue with police," a spokesman said.

Etihad Stadium and the MCG said they were reviewing security measures.

"People coming to the MCG this weekend should do so in the knowledge that providing a safe and secure environment remains our top priority," an MCG spokesman said.

Nicola Palfrey, director of the Australian National University's Child and Adolescent Trauma, Loss and Grief Network, said the attack was a "watershed moment" that would undoubtedly deter young event-goers.

"We haven't had an event that has so explicitly targeted young people so it may well encroach on young people's sense of their own safety," she said.

"There is a tipping point at which people will start to get spooked at these sorts of events and it seems you can't get much more innocent than taking your children to an Ariana Grande concert. Unfortunately I think this is a bit of a watershed."

Clinical psychologist Dr Vicki Trethowan said parents now face a difficult prospect if their child wants to go to a concert but she encouraged them to keep perspective and not instil fear in everyday life.

"You want to be vigilant but you want children to feel that they can still engage in activities that children like to engage in," she said.

She recommended limiting kids' exposure to news, speaking in their language and reassuring them that adults are trying to keep them safe.

Mr Sheridan, the former NSW Police commander for major events, said it is difficult to secure every area around a stadium but Australian event organisers were world leaders at responding to emerging threats.

The federally-funded Australian Child and Adolescent Trauma, Loss and Grief Network has resources on helping children to process disasters.