The ABC understands the alleged cell was capable of making an improvised explosive device, and police have found materials and items that could be used to make a homemade bomb.
Mr Turnbull said the raids had been a "major joint counter-terrorism operation".
None of the four suspects arrested in five raids had been charged, Colvin said.
An "explosive device" was discovered at the Surry Hills property and deactivated by a bomb squad, according to The Seven Network.
Australia, a staunch ally of the US, has been on heightened alert for attacks by homegrown militants returning from fighting in the Middle East, or their supporters, since 2014.
The plot was the 13th significant threat disrupted by police since Australia's terrorist threat level was elevated in 2014, Justice Minister Michael Keenan said.
"Come into the city, take your trains, go to the shops, you shouldn't be concerned in relation to this", he said.
Neighbours described the man's parents as a "lovely couple" who held barbecues every Sunday.
"The primary threat to Australia still remains lone actors", he said.
A Qantas spokesperson - representing Qantas and Jetstar - said it was working closely with the Government and airport partners to implement the measures.
Five properties in Sydney suburbs were raided on Saturday evening.
A northern section of the road was blocked off for much of the night, but neighbours were allowed to return to their homes about 10.30pm.
The prime minister said there was "more in that category of an elaborate plot" rather than a more amateur attempt.
'These operations are designed to disrupt and prevent plans to undertake terrorist attacks in Australia, ' the statement said. That investigation involved a conspiracy to blow up public spaces in NSW and Victoria.
Travellers in Australia are being told to arrive early for flights after plot to 'bring down plane'.
He said extra security was in place at domestic and international airports.
Dr Coyne agreed current provisions would have thwarted the plot had it gained momentum.
He was then asked why he was arrested, to which he mumbled "I don't know nothing".
Cleveland St remained closed to traffic last night as crime scene officers seized evidence and took photographs as they moved through the house.
- Los Lakers buscan más estrellas
- Griezmann, el mejor futbolista francés del 2016
- Corea del Norte lanza un misil mejorado con posible alcance intercontinenal
- Sharif's disqualification: ECP expected to announce schedule for holding by-polls
- Un muerto y tres heridos por tiroteo en Constanza, Alemania
- Táchira: queman puestos de votación para Asamblea Constituyente
- Se vuelca camión con 33 pacientes del IMSS en carretera de Sonora
- Tempranero gol de Pabón da el triunfo a Rayados de Monterrey
- Xi exige compromiso al Ejército chino en pro de la paz
- La historia real detrás de Molly’s Game