(Bloomberg) -- Authorities ramped up security at all major Australian airports after counter-terrorism police thwarted an alleged plot to bring down a plane.
Officers raided homes in several Sydney suburbs on Saturday and arrested four men after uncovering plans to carry out an attack with an improvised device, according to police, who believe the suspects were inspired by the Islamic State militant group.
Air passengers were advised to limit their carry-on and checked baggage and expect delays caused by additional security measures. Security was tightened at Sydney airport, the nation’s busiest hub, on Thursday, with measures extended to all major international and domestic terminals across Australia on Saturday night.
Prime Minister Malcolm Turnbull said authorities had acted swiftly to disrupt a sophisticated terrorism plot.
“They were very advanced,” Turnbull told Australian Broadcasting Corp. radio on Monday. “The police will allege they had the intent and were developing the capability.” He declined to provide further details of the alleged plot, other than to say it had an “Islamist extremist terrorist motivation.”
The tightened security “may go on for some time yet,” Immigration Minister Peter Dutton told reporters in Melbourne on Monday. “We have foreign fighters returning to Australian shores, we’ve got people being radicalized online. This threat is not going away, it’s going to increase.”
Australia is a key ally of the U.S. and has flown combat missions against Islamic State in Syria. Australian intelligence services have disrupted or stopped at least a dozen major terrorism plots since 2014, including one last year that would have seen a bomb detonated in central Melbourne, according to the government.
In December 2014, two hostages and a gunman who’d claimed allegiance to Islamic State died after a siege in a Sydney cafe.
Australian Federal Police Commissioner Andrew Colvin on Sunday said officers are “investigating information indicating that the aviation industry was potentially a target” of the planned attack. He declined to discuss potential charges that the four men in custody might face. None of the men worked in the airport industry, he said.
The nation’s terrorism threat level remains at “probable,” the third-highest setting on a five-point scale.
Qantas Airways Ltd. said it’s working closely with the government and its airline partners to boost security.
“We appreciate the understanding and patience of passengers as we implement these enhanced security measures,” Qantas said in an email. “Australia has very strong safeguards in place at its airports; these changes are about making them even stronger.”
Virgin Australia Holdings Ltd. advised passengers to expect increased scrutiny.