Four people have been arrested in late night raids by Australia's counter-terrorism task force over an alleged plot to blow up a passenger plane, Prime Minister Malcolm Turnbull has confirmed. The federal police believes the planned attack was “Islamic-inspired terrorism.”

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Police have obtained information that “some people in Sydney were planning to commit a terrorist attack using an improvised devise,” Australian Federal Police Commissioner Andrew Colvin told reporters.

The plot is believed to be related to “Islamic-inspired terrorism,” Colvin said. He did not specify if any terrorist groups, such as Islamic State (IS, ISIS/ISIL), have been linked to the foiled attack.

BREAKING: Australia disrupts terror plot to bring down airplane, according to Prime Minister; 4 arrested in #Sydney raids pic.twitter.com/HM3qDzSX53 — Amichai Stein (@AmichaiStein1) July 29, 2017

The federal police are “investigating information indicating the aviation industry was potentially a target of that attack,” Colvin added.

He said there was no indication that airport security was “compromised” at any time.

"Four men have been taken into custody and are assisting police with their enquiries," the Australian Federal Police said in a statement.

Statement from the Prime Minister on a counter terrorism operation in Sydney. Read more here: https://t.co/JfJi6UpQP0 — The PMO (@thepmo) July 29, 2017

"The public should be reassured that our security and intelligence agencies are working tirelessly to keep us safe," PM Turnbull said in a statement earlier.

Security at Sydney airport was stepped up Thursday in anticipation of a potential attack, with similar measures implemented at airports across the country.

Australia's terrorism threat remains at the same “probable” level as it was prior to the raids.

Turnbull advised travellers to expect delays due to increased airport security but said there was no imminent danger.

"Some of the measures will be obvious to the public, some will not be — those travelling should go about their business with confidence," Turnbull said, as cited by Reuters.

"The office of transport security has advised security screening will take longer, and travellers should arrive at terminals at least two hours before flights to allow ample time for screening.

"They should limit the amount of carry-on and checked baggage, as this will help to ensure that security screening is efficient."

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Last week, Turnbull released an online video statement in which he announced major reforms of Australia’s counter terrorism agencies.

Bomb defused at property, several detainees injured – reports

With little information released by police on the suspects, some details of the counter-terrorism operations have emerged in media reports.

Following a raid in Sydney’s eastern suburb of Surry Hills, a man was escorted from a house with a white sheet covering his head and shoulders. His head was wrapped with a bandage.

Before being driven away in an ambulance the man told journalists gathered at the property, that he had “no idea” what he was suspected of. “They bashed me,” he said, referring to the police arrest.

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An elderly woman wearing a hijab, with her face covered with a jacket, was also seen being ushered from the property by police. Another woman with her hands tied up was treated by the medics at the scene, The Daily Telegraph reports. It was unclear if any of the women would be charged. Witnesses cited by the outlet said they heard loud screams during the operation that reportedly involved around 40 armed riot police, who stormed into the house from both front and back, smashing a part of a back fence, The Sydney Morning Herald reported.

A bomb disposal unit was called to the scene and a street near the property was briefly sealed off. With no official confirmation forthcoming, Australia’s Channel 7 reported that an explosive device was discovered.

Another police raid was conducted at a property located in Wiley Park, a suburb in south-western Sydney. According to neighbors, the man detained by police was aged around 50, lived with his brother, enjoyed an occasional family visit and had a thing for cats; keeping over a dozen of felines at home.

“He was a strange man, he never looked at you in the eye when you spoke to him,” one of the neighbors told the Daily Telegraph.

In Punchbowl, also in south-western Sydney, police reportedly raided a home of a Lebanese family. Eyewitnesses said they heard a woman screaming and saw police questioning four women and a wheelchair-bound man.

“We don’t really know them, we just say hi because they’re Lebanese as well. They seem like good people,” neighbors were cited as saying.

Another raid was conducted at Lakembam, south-western Sydney. Police were seen with gas masks as they entered the property but no further details were released.