Hundreds of police have carried out pre-dawn counter-terrorism raids across Sydney and Brisbane on Thursday.
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Police have carried out a major anti-terrorism operation across Sydney and Brisbane early on Thursday morning.
Hundreds of officers have raided homes across western Sydney and Brisbane's south.
More than 10 people have been arrested.
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In Sydney, the raids occurred in:
Beecroft, Bellavista, Guildford, Merrylands, Northmead, Wentworthville, Marsfield, Westmead, Castle Hill, Revesby, Bass Hill and Regents Park.
The raids in Brisbane were in:
Upper Mount Gravatt East, Logan, and Underwood
Operation Appleby #Sydney arrests #sydneyarrests pic.twitter.com/JfM77Mt5UM — NSW Police (@nswpolice) September 17, 2014
NSW Police Commissioner Andrew Scipione has arrived at the Sydney Police Centre in Surry Hills for a briefing on Thursday's raids.
"Today's operation reflects the challenges that we face," Mr Scipione said.
"This has been a big operation and it reflects what we are dealing with right now."
Mr Scipione and Australian Federal Police Acting Commissioner Andrew Colvin are due to provide an update on the operation at 9.30am.
A number of residents in the suburbs where the raids took place were woken by circling helicopters just after 4am.
One resident, Mark Anderson, told Fairfax Media he heard police officers on a loudspeaker asking someone to come outside a home in Guildford.
"I heard them calling out to him to 'Come out!' for about 10 to 15 minutes. I don't know if he was too agreeable. I didn't really understand a name. It was pretty intense," Mr Anderson said.
"It was a pretty big deal at our place. Early last night a helicopter hovered over here for a bit as well, then this morning it all kicked off."
In Bass Hill, Chris said he was woken by a helicopter hovering over his home at 4am. He went outside to find up to 40 police officers swarming his street.
"I went out to be a stickybeak, as you do, and I was told quite promptly: 'Go, go back inside, do not come out'," he told Triple M.
"Looking around, they had blocked off the road. It was only six doors down. It was pretty surreal."
Photographer Nick Moir is at the scene of one of the raids in Guildford.
It's believed the raids in Sydney were pre-emptive in nature, amid fears there were plans to carry out a series of attacks in Australia, AAP is reporting.
The arrests in Sydney follow months of surveillance of people linked to the terrorist group Islamic State, it said.
About 600 state and federal police, as well as ASIO officers, are involved in the Sydney operation, which is on-going.