Live: multiple explosions rock airport and metro stationThreat in Europe now 'beyond control' of authorities
Prime Minister Malcolm Turnbull has criticised Europe's border protection measures in the wake of the atrocities in Brussels, arguing Australia is more secure because of its strong borders and geographic isolation.
Extending "our most resolute solidarity" to the Belgian people, Mr Turnbull nonetheless said Europe had "allowed their security measures to slip" and that this was "a lesson for all of us". He was critical of the Schengen agreement that enables free movement within Europe, as well as the "very porous" external borders that encouraged entry to the continent. 
"There's been a real breakdown in intelligence. If you can't control your borders, you don't know who's coming or going. Regrettably they allowed things to slip and that weakness in European security is not unrelated to the problems they've been having in recent times," he told ABC television.
"Europe has for all intents and purposes no internal borders, so people can travel within Europe as they wish, and their external borders have been very porous - as we've been seeing every night on the news. So Europe has a security challenge or a security problem that is different to Australia. We're assisted by our geography, of course, but we also have very strong border protection that our government has maintained."
The bomb blasts at Brussels' airport and a railway station come four months after a series of co-ordinated terror attacks in Paris, killing 130 people and setting in train a manhunt that has frequently led authorities into Belgium. Salah Abdeslam, a key suspect in those attacks, is a Belgian-born French national who was arrested in Brussels last week.
The Prime Minister said that while Australia's border protection measures helped identify and repel threats to national security, there was no guarantee we could avoid similar atrocities.
"We have a much greater insight into people who we would regard as being threats or likely to pose a risk ... than the Europeans do," Mr Turnbull said. "We obviously cannot guarantee that there will not be terrorist incidents in Australia - that's why the threat level is 'probable' - nevertheless we have very strong measures in place."
An early morning teleconference took place between Mr Turnbull, Attorney-General George Brandis and security chiefs including the acting director-general of security, Australian Federal Police Commissioner Andrew Colvin and counter-terrorism co-ordinator Greg Moriarty. ASIO's advice was that the terror threat level should remain at the third-highest level, "probable", Mr Turnbull said. Another meeting would be convened later on Wednesday.
Border protection staff at Australian airports are due to strike on Thursday as part of an ongoing dispute over pay and conditions. The PM said he would "strongly encourage" the Community and Public Sector Union to rethink the planned industrial action, but insisted security at airports would not be undermined because it was chiefly the responsibility of the AFP not the Australian Border Force.
Mr Turnbull joined US President Barack Obama in citing the attacks in Brussels - which left at least 34 people dead and 250 injured - as another reminder of the need to unite against international terrorism. Islamic State has claimed responsibility.
"We are in a battle with these terrorists and we will defeat them," Mr Turnbull said. "Our enemies, these terrorists, are very, very agile. We have to be as agile as them, we have to respond quickly and innovatively to the threats as they emerge."
Australians should reconsider their need to travel to Belgium, while those already in the country should follow local advice, the PM said.
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