Arrests Over Deadly Australia 'Terror' Attack

Four people have been arrested over the murder of a police accountant in Australia which investigators think was terror-related.

Detectives believe the suspects, aged from 16 to 22, were involved in planning the killing of Curtis Cheng as he left police headquarters in the Sydney suburb of Parramatta on Friday.

The 58-year-old, who had been with the police force's finance department for 17 years, was shot in the back of the head by Farhad Jabar Khalil Mohammad.

The 15-year-old gunman, who was born in Iran, was shot and killed at the scene by police.

The investigating team have also contacted Turkish police to search for the killer's sister, who left Australia the day before the deadly attack.

New South Wales Police deputy commissioner Catherine Burn said: "We suspect that a terrorism event has occurred and we suspect that they may have some knowledge.

"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."

Jabar was not under surveillance and was not considered a threat.

However, some of those detained on Wednesday were the target of anti-terrorism raids a year ago, deputy commissioner Burn said.

Some 17 people were held at the time, which police said prevented a beheading plot.

Police have already arrested a 17-year-old boy on his way to the school were Jabar was a pupil, charging him with offences linked to the use of social media harass and intimidate.

Australia has been struggling to cope with a number of home-grown terrorist attacks over the last year.

An 18-year-old was shot dead by police after stabbing two counter-terrorism police officers in Melbourne, while a gunman and two hostages were killed in a cafe siege in Sydney.

In April, several teenagers were held on suspicion of plotting an Islamic State group-inspired attack at a Veterans' Day ceremony while in May, a 17-year-old was arrested in Melbourne, accused of plotting to detonate three homemade pipe bombs.