Radicals praise hit on Australia police

Victim Curtis Cheng (standing far left) had been working with the NSW Police Force for 17 years. Photo / Supplied

Supporters of Isis (Islamic State) have praised the deadly attack on New South Wales police headquarters, extolling 15-year-old Farhad Khalil Mohammad Jabar as a "knight" who had carried out a mission on behalf of the terrorist group.

The attack in Parramatta on Friday, in which 58-year-old NSW police accountant Curtis Cheng was shot dead, has also prompted calls for more so-called lone-wolf attacks.

A supporter of the terror group has also claimed on social media that Jabar's passport had been seized by authorities prior to the attack.

"Farhad Muhammad. His family had been raided several times, his mother humiliated, his passport taken ... " the person claimed.

The claim has not been verified and AAP has contacted NSW Police, the Department of Foreign Affairs and Trade and the Attorney-General's Department for comment.

"They were under constant surveillance so our brother, Farhad, took a stand and attacked a Police HQ," the user wrote.

The person tweets in English and Arabic and appears to have connections to the United Kingdom.

"Allah accept our brother Farhad Mohammed - 15 years old. Killed one officer. Then got shot, to his shahada inshallah. He struck terror right in the HEART of the disbelievers."

This comes amid reports Australian counter-terrorism authorities have linked the 15-year-old with a British radical associated with Isis. The report has not been confirmed.

Another supporter, known as Abu Abdullah, called for the killing in Parramatta to inspire similar attacks.

- AAP