He was talking after four individuals were captured in strikes crosswise over Sydney.
Specialists said they had seized materials in the assaults that could have been utilized to make an ad libbed hazardous gadget.
Mr Turnbull said the strikes had been a “noteworthy joint counter-psychological warfare operation”.
He said additional security was set up at household and global air terminals.
The assaults occurred in the Sydney rural areas of Surry Hills, Lakemba, Wiley Park and Punchbowl, Australian telecaster ABC revealed.
Australia’s national fear risk level stays at “likely”.
Police closed streets following the assaults crosswise over Sydney
Australian Federal Police Commissioner Andrew Colvin said the four men captured were professedly connected to an Islamist-propelled plot.
“Lately, law implementation has turned out to be mindful of data that proposed a few people in Sydney were wanting to submit a psychological militant assault utilizing an IED (ad libbed dangerous gadget),” he told a news gathering.
He said police did not yet have data on “the particular assault, the area, date or time”, including that he anticipated that the examination would be “long and extended”.
ABC revealed that a lady in the Surry Hills range, who said her child and spouse had been captured, denied that they had any connects to fear based oppression.
June 2017: In Melbourne, shooter Yacqub Khayre murders a man and holds a lady prisoner amid an attack at a condo building. Three cops are harmed after Khayre connects with them in a firefight. He is shot dead.
December 2016: An expansive police operation thwarts a fear plot to bomb points of interest in Melbourne on Christmas Day. Head administrator Malcolm Turnbull portrays the arrangement as an “Islamist fear based oppressor plot”.
September 2016: Police charge a 22-year-old man with submitting a fear based oppressor act and endeavored kill in southwest Sydney. They say he was roused by the Islamic State (IS) gathering. Officers say the aggressor more than once wounded a 59-year-old man in a rural stop and after that endeavored to cut a policeman.
October 2015: Fifteen-year-old Farhad Jabar Khalil Mohammad shoots a non-military personnel worker of the New South Wales Police dead before being slaughtered by constables at the police home office in Parramatta, Sydney.
December 2014: Man Haron Monis, a so called priest initially from Iran, takes 17 individuals prisoner in a bistro in the focal point of Sydney. Monis and two prisoners are killed following a 16-hour attack. A therapist later tells an investigation into the attack that Monis had an extreme identity issue that empowered him to incur tremendous mischief on others.