Roundup: 5 people arrested in Sydney terror-related raids

Three of the five the suspects arrested in counter-terrorism raids in Western Sydney on Wednesday had been previously targeted in Australian counter-terrorism operations in September.

More than 200 police officers and counter-terrorism authorities raided four properties across western Sydney, detaining five suspects for questioning.

It is believed one or more of the men were also subjects of targeted raids in September by counter-terrorism authorities as part of Operation Appleby.

The fifth man, 24, was not detained as part of the counter- terrorism operation but as result of an outstanding warrant for identity and fraud matters, the Australian Federal Police said in a statement.

The four men may hold the key investigators are seeking to piece together the events that led to the terrorist attack by 15- year-old Farhad Khalil Mohammad Jabar outside the Parramatta Police station last Friday.

"Let me say that today's operation is a clear indication of our determination to actually find out who murdered Curtis Cheng and to take all necessary action that we possibly can," Burn told A media conference in Sydney.

"It's a very, very serious concern that in the heart of our community there is attack planning that is underway and that may have led to what we saw on Friday."

Jabar, a teenager of Iraqi-Kurdish decent but born in Iran, gunned down Cheng, a 17-year veteran of the police force's finance department, outside the Parramatta Police Station which houses some of the state's top detectives on Friday afternoon.

"This is a terrorist incident. That's what it is, there is no doubt about it," New South Wales (NSW) Premier Mike Baird told reporters on Wednesday.

"We have to ensure that we don't see incidents like this again and we're doing everything we possibly can to ensure that."

Burns conceded however Jabar was not on counter-terrorist authorities' radar despite his alleged links to those targeted in the September raids and "not somebody we would have assessed as a threat."

"It's difficult because we don't really know the motivation of the 15-year-old," Burn said. "What we would suggest, and we suspect, is that there was some influence, whether it was ideologically, religious or politically motivated, that determined and influenced the 15-year-old to go and commit this horrendous act of violence."

Asked if the teenager should have been on the radar of Australia's counter-terrorism authorities, Burn said "time will clearly tell."

"For 24 hours 7 days a week, people go and do certain things and it's a reality of life we can't be everywhere with everybody at every single second of the day."

Jabar's sister is believed to have flown from Sydney to Turkey via Singapore in the days before he carried out the terrorist attack.

Australian authorities are in contact with Turkish national police to try to establish her whereabouts, though stressed it is not suggested she was involved in any criminal activity in Australia.

"But obviously investigators are very keen to have a chat with her about what she knows about her brother's action," police Acting Deputy Commissioner Neil Gaughan said.

Gaughan declined to speculate on any links to Islamic State either the group or Jabar have.

"We are focusing on the murder of the innocent person killed in Parramatta on Friday," Gaughan said.

"Whether or not there is international groups (involved), we'll get to that. But at the moment we need to focus on this issue and resolve it."

Wednesday's raids follow the arrest of a 17-year-old teenager on Tuesday who attends the Arthur Phillip High School in western Sydney, the same school as Jabar, for threatening police after posting his support for Cheng's brutal murder on social media.

Local media has also reported two of those detained following the counter-terrorism raids attend or attended the same school.

When asked if he was concerned about radicalisation of school children, NSW Premier Mike Baird assured that the state's schools are safe.

"We need to understand we are in a new world," Baird said. "The risks that are emerging are new."

Baird said while there had been some isolated incidents, "they are being dealt with by police, they are being dealt with by the Department of Education together and that's what we continue to see."

"Certainly my strong assurance to the people of NSW is that our schools are safe."

Baird said his government has been working on programs to combat radicalisation that will be released in the near future.

"We need to provide more support, undoubtedly into our schools to deal with what is a new threat," Baird said. "This threat, that is new here, is new across the world."

Authorities remain unsure how Jabar managed to procure a firearm, however they aren't ruling out it being supplied by the group detained or another member of the public.

"The supply of the firearm is a major part of our investigation and that is a line of inquiry we'll be undertaking with these people today," Burn said. Endi