Police patrol at Sydney airport (Photo: www.rte.ie)

Australian Prime Minister Malcolm Turnbull said on Sunday that airport security would also be screening baggage more closely in the wake of the foiled plot, urging passengers to limit their carry-on and checked luggage to "necessary items" to avoid delays. Passengers were asked to arrive two hours before their flights in case of further disruption.

Prime Minister Malcolm Turnbull and Border Protection Minister Peter Dutton declined to comment on newspaper reports that Islamist extremists planned to kill the occupants of a plane with poison gas and that a homemade bomb was to be disguised as a kitchen mincer.

Four men arrested in raids in Sydney late Saturday — two Lebanese-Australian fathers and their sons — had yet to be charged.