Australia ramps up airport security after alleged plane bomb plot

Stricter screening of passengers and luggage at Australian airports, introduced after police foiled an alleged "Islamic-inspired" plot for a bomb attack on a plane, will remain in place indefinitely, Australia's immigration minister said today.

The ramped up security procedures were put in place after four men were arrested at the weekend in raids conducted across several Sydney suburbs.

The men are being held without charge under special terror-related powers. The Australian Federal Police would not confirm media reports the alleged plot may have involved a bomb or plan to release poisonous gas inside a plane.

The arrests follow last month's siege in the city of Melbourne, where police shot dead a gunman who was said to have links to the Islamic State group.

Immigration Minister Peter Dutton told reporters in Melbourne today that the alleged plane bomb plot could prompt longer-term airport security changes.

"The security measures at the airports will be in place for as long as we believe they need to be, so it may go on for some time yet," Dutton said.

"It may be that we need to look at the security settings at our airports, in particular our domestic airports, for an ongoing enduring period."

Inter-state travellers are subjected to far less scrutiny than those travelling abroad with no formal identification checks required for domestic trips.

Passengers at major Australian airports, including Sydney, experienced longer-than-usual queues during the busy Monday morning travel period. A Reuters witness said the queues had disappeared at Sydney Airport by lunch-time.

A source at a major Australian carrier said airlines and airports had been instructed by the government to ramp up baggage checks as a result of the threat, with some luggage searches now being conducted as passengers queued to check in their bags.