Two words teenage boy yelled after allegedly stabbing Sydney bishop at Wakeley, Sydney church

The 16-year-old boy who allegedly stabbed a bishop in an act of terrorism justified his actions by telling witnesses the Christian leader had 'sworn' at one of his prophets and screamed 'Allahu Akbar'  after plunging a knife into his face.

Bishop Mar Mari Emmanuel was attacked while delivering a sermon in the Christ the Good Shepherd Church in Wakeley, in Sydney's west, on Monday night. 

Horrified parishioners leapt into action, with some rushing to the bishop's aid and others helping to detain the teenager inside the church. 

In video of the stabbing, the 16-year-old is heard telling church-goers in Arabic: 'If he didn't swear at my Prophet I wouldn't be here. If he didn't involve himself in my religion I wouldn't be here'. 

One of the men involved in restraining the teenager after the attack told a police officer how he approached the teen from behind and forcefully pushed him to the ground. 

'He kept saying: 'Allahu Akbar, Allahu Akbar',' he tells the officer in a video posted to social media.

AFP Commissioner Reece Kershaw was asked to confirm the teenager's religion amid speculation he had recently converted to Islam.

'We have a lot of intelligence to go through and confirm,' he said.

'I can't go through that. One of the things I want to say it's a disgraceful act from the community who attacked police at that scene.'

ASIO boss Mike Burgess was asked if he was aware of the comments and if the bishop had said or done anything to trigger the attack. 

'We're aware of those comments and everything else is open inquiry lines to understand why the individual got to where he did,' he said. 

Mr Burgess was asked why the incident in Wakeley was considered a terrorist attack while the stabbing in Bondi Junction wasn't. 

'The simple answer there is to call it a terrorist attack you need indications of, information or evidence that suggests actually the motivation was religiously motivated or ideologically motivated,' he said. 

'In the case of Saturday that was not the case. In this case [Wakeley] information that we and the police have before us it would indicate strongly that is the case and that's why it was called an act of terrorism.'

Mr Burgess said ASIO would 'look at individuals connected with the attacker to assure ourselves there's no one else in the community with similar intent'.

The spy boss added: 'At this stage, we have no indications of that. 

'But it's prudent that we do this to determine there's no threats or immediate threats to security. At this time, we're not seeing that.'

Prime Minister Anthony Albanese in condemning the violence said the National Security Committee had held a meeting on Monday night. 

He said a joint counter terrorism taskforce had been established with the AFP and the Australian Security Intelligence Organisation. 

NSW Police Commissioner Karen Webb on Tuesday declared the attack was a terrorist incident 'centred around religion'.

 Police confirmed one of the alleged 16-year-old attacker's fingers was cut off after he was pulled away from the bishop.

It had been speculated a member of the angry mob had been responsible but it is now understood he accidentally severed the finger himself during the alleged attack. 

Pictures which showed all four fingers on the left hand severed are understood to be fake. 

'People were vomiting from the pepper spray and running into people's homes to get water,' he said.

He blamed the power of social media for how things escalated so severely.

'If it wasn't for social media the police would have arrived before the people rioting and this wouldn't have happened,' he said.

'They wanted blood. It was a great build-up of mayhem.

'My only concern was for the bishop's welfare. He is recovering but I don't think he'll be released from hospital any time soon.'

The 16-year-old boy is being kept at an undisclosed location under police guard.

He and the bishop underwent surgery on Tuesday morning.