Australian Prime Minister Malcolm Turnbull says police have broken up a terrorist plot to bring down an airliner after they raided several homes in the Sydney area and arrested four men.
"I can report last night that there has been a major joint counterterrorism operation to disrupt a terrorist plot to bring down an airplane,” Turnbull told reporters on July 30.
"The operation is continuing," he added.
The prime minister said additional security had been put in place at all major airports.
He said the alleged plan appeared to be "more in the category of an elaborate plot" than something that would be carried out by a so-called lone wolf.
Andrew Colivn, the Australian Federal Police commissioner, said details were not yet clear on the specific location and timing of the potential terror attack.
"In recent days, law enforcement has become aware of information that suggested some people in Sydney were planning to commit a terrorist attack using an improvised device," Colvin said.
"We are investigating information indicating the aviation industry was potentially a target of that attack," he added.
None of the four suspects detained has been charged, police said, and the men's identities were not released.