Australia's Prime Minister, Malcolm Turnbull, has confirmed police in Sydney last night disrupted a terrorist plot to bring down a plane.
Australian anti-terrorism police arrested four men during a series of raids in Sydney overnight.
Heavily armed police carried out raids at several properties, in the inner-city suburb of Surry Hills, and the southwest suburbs of Lakemba, Wiley Park and Punchbowl.
Federal police were given information the plot involved the use of an "improvised device".
A woman, who told the ABC her son and husband were arrested after her Surry Hills house was raided, denied they had any links to terrorism.
"I love Australia," she said as she was accompanied to a waiting car by police.
Meanwhile, additional security measures are now in place at Australian airports.
Mr Turnbull said passengers should allow extra time - at least two hours - for screening because of the additional security measures.
He said they should also cut down on their baggage.
Australia's terror threat level remains at probable.
In an earlier statement this morning, the Prime Minister's Office said the raids were "designed to disrupt and prevent plans to undertake terrorist attacks in Australia".
"I have been kept closely briefed on the progress of the operations by the heads of our relevant security agencies," Mr Turnbull said.
"However, as the operations are ongoing, it is inappropriate to provide further detail at this stage."
Photo: AFP Malcolm Turnbull says additional security measures are now in place at Australian airports.