A teenage boy faces a possible term of life in prison after being charged with a terrorism offence for the stabbing of a bishop at a western Sydney church.

The 16-year-old is accused of attacking Bishop Mar Mari Emmanuel during a live-streamed sermon at Christ the Good Shepherd Church in Wakeley on Monday night.

Investigators from a joint counter-terrorism team, incorporating state and federal police and ASIO staff, interviewed the boy in his hospital bed on Thursday before charging him with committing a terrorist act.

The Commonwealth offence carries a maximum penalty of life imprisonment.

The teenager has been refused bail and is expected to face a bedside court hearing in Sydney on Friday.

Australian Federal Police Commissioner Reece Kershaw said investigators believed the attack met the criteria of a terrorism act, but refused to go into further detail.

Authorities have said the stabbing was declared a terrorist act because of the teenager’s suspected religious motivation.

The boy travelled 90 minutes from his home to the church before stabbing Bishop Emmanuel up to six times, causing serious lacerations to his head, Mr Kershaw said.

The teenager was also injured during the attack and its aftermath.The teenager allegedly made comments in Arabic that referred to insults against “my Prophet” before stabbing Bishop Emmanuel, who has publicly criticised Islam and other religions.

Leaders from the Lebanese Muslim community in Sydney have said the 16-year-old’s family did not believe he had been radicalised online before the attack.

The charge comes as police hunt for as many as 50 people involved in a riot that unfolded after the incident at the Assyrian church.

Dozens of police were injured, their cars vandalised and a cohort of officers and paramedics were forced to shelter inside the place of worship, prompting religious leaders to call for calm.

NSW Police Commissioner Karen Webb said extra police were out in force with a high-visibility operation “for as long as needed to reassure the community we are there to keep them safe”.

“We have deployed extra officers since Monday night particularly in southwest Sydney but across Sydney to patrol places of worship,” she said.

“The community should have no concerns for their safety.”

In an audio message on Thursday Bishop Emmanuel said he forgave his attacker and called on his followers to obey the law.

“I need you to act Christ-like, the lord Jesus never taught us to fight,” he said in the message from hospital.

Dani Mansour, 19, from Doonside, was the first person to be charged over the public disorder incident.

He appeared in court on Thursday, saying he made a mistake but he was “pissed off” at officers who had hurt people outside the church.

He allegedly filmed himself kicking two police cars during the riot before uploading the footage to Instagram.