Five men were arrested in Australia Wednesday over the fatal terror-linked murder of a police employee after raids by more than 200 police on properties across Sydney.

Five men were arrested in Australia Wednesday over the fatal terror-linked murder of a police employee after raids by more than 200 police on properties across Sydney.

The operation followed Farhad Jabar, 15, shooting 58-year-old Curtis Cheng in the back of the head outside New South Wales state police headquarters in the city's west on Friday.

"Five people have been arrested in relation to the fatal shooting of Curtis Cheng outside police headquarters at Parramatta on Friday October 2," police said in a statement after the early morning raids.

"The five men have been taken into custody and will be taken to various police stations where they will be interviewed in relation to Friday's fatal shooting."

The raids came a day after a student who attended the same school as Jabar
was arrested and charged over alleged posts on social media.

He was also charged with assaulting and intimidating police and resisting arrest while on his way to Arthur Phillip High School in western Sydney on Tuesday.

Authorities on Sunday searched a mosque the shooter is believed to have attended with the consent of religious leaders.

Australian officials have said they are concerned about the prospect of lone-wolf attacks by individuals inspired by groups such as the so-called 'Islamic State of Iraq and the Levant' (ISIL) takfiri group, and have cracked down on Australians attempting to travel to conflict zones such as Syria and Iraq.