Four men were arrested during raids on homes in several Sydney suburbs on Saturday in connection with a plan to bring down an airplane. Australian Prime Minister Malcolm Turnbull said security measures had been intensified at Sydney Airport because of the plot.
"I can report last night that there has been a major joint counterterrorism operation to disrupt a terrorist plot to bring down an airplane. The operation is continuing."
Australian Federal Police Commissioner Andrew Colivn said details about the specifics of the planned attack--including timing and location--remain scare.
"In recent days, law enforcement has been become aware of information that suggested some people in Sydney were planning to commit a terrorist attack using an improvised devise," Colvin said.
"We are investigating information indicating the aviation industry was potentially a target of that attack," he added.
As a result of the increased security measures, Turnbull advised travelers in Australia to arrive at airports two hours earlier than usual to allow for extra screenings.
According to Justice Minister Michael Kennan, the plot was the 13th significant threat disrupted by police since the country's terrorist threat level was increased in 2014. Five plots have been executed.
"The primary threat to Australia still remains lone actors, but the events overnight remind us that there is still the ability for people to have sophisticated plots and sophisticated attacks still remain a real threat," Keenan said." In light of this information, it's very important that everyone in Australia remains vigilant."
Squad officers were seen wearing gas masks as they stormed an inner-Sydney house before an explosives team located a suspicious device.
As of Saturday night, police said the four suspects have not been charged.
The Associated Press contributed to this report.