Police raid properties, airport security increased after terror plot foiled

July 31 (UPI) -- Australian police said officers launched raids on at least five properties in Sydney on Monday, after four men were arrested over the weekend for a terrorist plot to bomb a commercial airliner.

The men were arrested on Saturday following previous raids in Sydney's suburbs of Surry Hills, Lakemba, Wiley Park and Punchbowl. Australian Federal Police said officers seized materials that could be used to make an improvised explosive device.

AFP investigators are expected to gather more evidence from the properties raided on Monday for several days. The four detained men, who local media report include a father and his son, can be held for up to seven days without charge after police were granted additional counter-terrorism powers.

AFP Commissioner Andrew Colvin said the arrested men were linked to an Islamist-inspired plan to detonate an explosive aboard a plane, but he said police did not yet have information on "the specific attack, the location, date or time."

Colvin on Monday said no official details have been released yet amid theories of what type of explosive device would have been used in the attack.

"The plot that we are investigating we believe was an attempt to put a device onto an aircraft, but beyond that the speculation is just that -- it's speculation," Colvin told a press conference.

Colvin said additional security measures have been put in place in Australia's airports following the thwarted attack.

"What people can expect is there's an increased police and security agency presence. You can expect longer delays to make sure that more screening is being done on baggage," he said.

Australian authorities have not yet revealed the identities of the suspects.

On Sunday, Australian Prime Minister Malcolm Turnbull confirmed authorities foiled the plot.

"My number one priority, and that of my government, is the safety and security of all Australians," Turnbull said in a televised news conference. "The public should be reassured that our security and intelligence agencies are working tirelessly to keep us safe."

Australian Justice Minister Michael Keenan said the plot was the 13th significant threat neutralized by authorities since the country raised its terrorism threat level from "medium" to "high" in 2014.

Ben Hooper contributed to this report.