Airport security stepped up after plot to 'bring down' a plane in a terrorist attack in Australia

AAP

Prime Minister Malcolm Turnbull has said counter-terrorism agencies foiled a plot to "bring down" a plane in an Isis-inspired terrorist attack and Australian airport security measures across the country have been heightened as a result.

Four men were taken into custody on Saturday night when heavily armed counter-terrorism officers raided four Sydney properties over an alleged plot that reportedly involved blowing up an aircraft.

Mr Turnbull said increased security measures have been placed on all Australian airports.

"Those travelling should go about their business with confidence," he said.

TV footage shows a man with a bandage on his head and draped in a blanket being led away by authorities. Photo: 7 News

"But the Office of Transport security has advised that 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 security screening is efficient."

Australian Federal Police, NSW Police and the domestic spy agency ASIO jointly carried out the major counter terrorism operation in Surry Hills, Lakemba, Wiley Park and Punchbowl.

TV footage shows a man with a bandage on his head and draped in a blanket being led away by authorities.

Prime Minister Malcolm Turnbull has been briefed on the progress of the operation by security agency heads. Photo: AAP

The family who lived in the raided house on Cleveland Street in Surry Hills has been described as "perfectly nice and normal people" Photo: 7 News

Prime Minister Malcolm Turnbull has been briefed on the progress of the operation by security agency heads.

"These operations are designed to disrupt and prevent plans to undertake terrorist attacks in Australia," the prime minister said in a statement.

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

The family who lived in the raided house on Cleveland Street in Surry Hills has been described as "perfectly nice and normal people" by a neighbour whose property backs onto theirs.

Australian Federal Police, NSW Police and the domestic spy agency ASIO jointly carried out the major counter terrorism operation in Surry Hills. Photo: AAP

"We knew them to say hello to and they seemed nice," the woman in her early 30s, who didn't want to be identified, told AAP.

An elderly couple lived in the home, the neighbour said, and they had adult children.

The neighbour came home while the raid was underway and said there were "heaps" of police at the scene.

Cleveland Street remains closed in both directions in Surry Hills between Elizabeth and Crown streets.

"Motorists are advised to avoid the area or allow plenty of extra travel time," a Transport Management Centre spokesman said in a statement.

Cleveland Street remains closed in both directions in Surry Hills between Elizabeth and Crown streets. Photo: AAP