A knife attack at a western Sydney church allegedly committed by a teenage boy, is being considered a "terrorist act" by police.
A 15-year-old boy is in custody on Tuesday after the overnight attack at Christ the Good Shepherd Church in Wakeley where Bishop Mar Mari Emmanuel was stabbed as the incident was broadcast on the church's livestream.
NSW Police Commissioner Karen Webb said the boy allegedly made comments as he launched the attack.
"After consideration of all the material, I declared that it was a terrorist incident," she told reporters on Tuesday.
NSW Premier Chris Minns said this is a "major and serious criminal organisation".
He acknowledged that Sydney was on edge following an unrelated stabbing attack in Bondi on the weekend but said anyone who engages in tit-for-tat violence would "be met with the full force of the law."
The footage showed a person dressed in black approaching and stabbing the bishop multiple times to the head and upper body at the altar as parishioners screamed and ran to the cleric's aid.
The suspect is "known to police" and not a regular attendee at the church. Source: Supplied / YouTube
"We'll allege there's a degree of premeditation on the basis this person has travelled to that location, which is not near his residential address, he has travelled with a knife and subsequently the bishop and the priest have been stabbed," Webb said.
"They're lucky to be alive."
Webb said the teenager was known to police but was not on a terror watch list. She added that the weapon had been described as a flick knife and detectives were investigating reports the boy lost fingers as part of the attack.
The attack led to street violence near the church where hundreds of people gathered and scores of police tried to disperse the crowd during which officers were injured and vehicles damaged.
Local federal member, Fowler MP Dai Le, has called for more police resources in the wake of the stabbing.
"I know that our police force here are under-resourced," she told ABC TV on Tuesday morning.
NSW Ambulance said they were called to the church about 7.15pm and sent multiple paramedics to the scene.
NSW Police said two clergymen were taken to hospital.
The church said Bishop Emmanuel and a senior priest were in a stable condition and also appealed for calm.
"We ask for your prayers at this time," the church said in a statement posted on social media.
"We also kindly ask anyone at the church to leave in peace as our Lord and Saviour, Jesus Christ, teaches us."
Source: Supplied / Facebook
The crowd continued to build outside the church and "a public order incident developed requiring police from all regions across Sydney".
Holland said more than 100 police officers and 30 police vehicles attended and the suspect was later removed from the church.
Two police officers were taken to hospital after being injured by members of the crowd who broke into "a number of houses to gain weapons to throw at the police".
Several police cars were damaged.
Holland said some in the group also threw items at the church in a bid to get access to the suspect.
"They need to let police do their jobs and let us do the investigation," he said.
"Police will make arrests in the future in relation to this public order incident," Holland said.
Readers seeking support with mental health can contact Beyond Blue on 1300 22 4636.
More information is available at
supports people from culturally and linguistically diverse backgrounds.
