Two knife attacks within three days - at a busy shopping centre near Bondi beach that killed six people on Saturday and at the Assyrian Christ The Good Shepherd Church in Sydney's west on Monday - has shocked residents of Australia's most populous city.

"I am doing fine, recovering very quickly ... there is no need to be worried or concerned," Bishop Mar Mari Emmanuel said in an audio message posted on social media, his first public comments since the attack. "I forgive whoever has done this act ... I will always pray for you and whoever sent you to do this, I forgive them as well."

Bishop Emmanuel, who has a popular youth following on TikTok and had criticised homosexuality, COVID vaccinations and Islam in his sermons, was injured in the attack, which has been deemed a terrorist act motivated by suspected religious extremism.

A male teenager has been arrested in the attack on the bishop and is in the hospital under police guard.

An angry crowd fought emergency crews outside the church, demanding that the suspected attacker be handed over to them.

New South Wales state Police Commissioner Karen Webb said a 19-year-old man, who was not a member of the church, was charged in connection with his role in the riot.

"People just came along to participate in a riot. That is disgraceful and disgusting," Webb said during a news briefing.

More detectives have been assigned to investigate the riot, which injured about 50 officers and damaged 20 police cars.

Bishop Emmanuel, in his message, urged his congregation to remain calm and respect the law.

As police investigate, the Bondi mall reopened on Thursday to allow people inside to pay their respects to the victims, with stores remaining closed and a white floral tribute laid out on the second floor. Businesses are expected to resume trade starting Friday.

"We've gone from shock to disbelief to now grief, and it's gonna take quite a time for people to be able to process," Paula Masselos, mayor of the local council, told ABC television.

A candlelight vigil will be held on Sunday, she said, as flowers and bouquets pile up at a makeshift memorial.

(Reporting by Renju Jose in Sydney; Editing by Gerry Doyle)

By Renju Jose