Screening at Australian airports has intensified and travellers should expect delays after authorities foiled a terrorist plot to bring down an aircraft using an improvised device.

On Saturday afternoon, NSW and Federal Police swooped on five properties in the Sydney suburbs of Surry Hills, Lakemba, Wiley Park and Punchbowl and arrested four men.

They are being held for an extended period under special legal conditions while investigators comb through evidence.

Travellers have been warned to arrive two hours earlier because of “additional scrutiny” and security experts say the arrangements will likely be in place for the foreseeable future.

Australian Federal Police commissioner Andrew Colvin said there was no indication the integrity of airport security had been compromised.