(BBC) -- Australian police have declared Monday's stabbing at a church in Sydney a "terrorist act".

A 15-year-old boy was arrested after a bishop and several churchgoers were stabbed during the sermon.

The incident happened in the evening at the Christ The Good Shepherd Church in the suburb of Wakeley.

At least four people were stabbed but police say none of their injuries were life-threatening. The incident triggered unrest.

Hundreds of people gathered outside the church, clashing with police - two of whom were injured.

Twenty police vehicles were damaged - with 10 left unusable.

Chief commissioner Karen Webb said those involved in the riots would be hunted by police, describing the actions as "unacceptable".

New South Wales Premier Chris Minns said: "I convened a meeting of faith leaders representing major religious organisations across Western Sydney.

"And their message to their communities was universal and identical, and that is that they deplore violence in all forms that they have faith in the New South Wales police to undertake their investigation.

"They call for peace amongst all communities in Sydney, and most importantly, that people remain calm during this obviously distressing period."

Paramedics had to retreat for cover in the church and were "holed up" there for more than three hours.