Australian security chiefs are on alert for further attacks as the stabbing of a bishop in Sydney is declared an act of terrorism.

A 15-year-old boy is accused of attacking Bishop Mar Mari Emmanuel, a senior figure in the ultra-conservative Assyrian Orthodox Church, and wounding three others during a live broadcast of a sermon.

At least 30 people, including two police officers, were injured when angry crowds congregated outside the church to demand vengeance on Monday night. 

NSW Premier Chris Minns said thousands of police officers were deployed to protect religious organisations and structures ‘‘in order to avoid retaliation or tit-for-tat violence”.

The incident has prompted the Australian Prime Minister, Anthony Albanese, his Deputy Richard Marles and Foreign Minister Penny Wong to convene for an emergency security meeting with the heads of the defence force and ASIO, the country’s spy agency. 

Karen Webb, the New South Wales Police Commissioner, confirmed on Tuesday morning that she had declared the alleged assaults at Christ The Good Shepherd Church a “terrorist act”.

“Strikeforce Katrina has been established to investigate that side of the events last night and a referral has been made and agreed to by the joint counter-terrorism investigation team,” Ms Webb said.

Noting the teenager had made comments “centred around religion’’ when he approached the bishop, she said investigators believe the incident could be considered ‘‘religious-motivated extremism’’. 

Police confirmed the boy was known to police, but ‘‘not well known’’.

“He wasn’t known to us from a terrorism point of view, he was not on any terror watchlist,’’ Ms Webb said.

“This is the first time this individual has come to our attention in this manner.”

Graphic footage captured during the Monday evening Mass showed a person dressed in black approaching the altar and launching a furious attack on the bishop’s head and upper body.

Father Isaac Royel suffered a shoulder wound and multiple lacerations when he tried to intervene to stop the attack, police will allege. 

Officers were later forced to barricade themselves and the suspect inside the church when hundreds of people gathered to demand vengeance for the stabbing, the second major knife assault in Australia in three days. 

Dominic Morgan, the state’s Ambulance Commissioner, said paramedics were ‘‘holed up in the church’’ for more than three hours during the violence which resulted in at least 30 people requiring medical treatment.

A police constable sustained a twisted knee and a chipped tooth after being hit with a metal object.

“Another constable sustained a broken jaw after he was hit with a brick and a fence paling,’’ NSW police said.

Two other men who intervened inside the church were treated in hospital for minor injuries.

The teen suspect underwent surgery on Monday night for a hand injury sustained when witnesses held him down on the floor. Rumours swirled amongst the community that the boy’s finger had been cut off. 

Acting Assistant Commissioner Andrew Holland said: “His injuries are quite severe in his hand, he’s fairly upset and fairly distraught.’’

In a post shared to the church’s Instagram page on Monday night, a spokesperson asked the mob of angry protesters to ‘‘leave in peace’’ and pray for both the victims and for the teenage suspect. 

“We ask for your prayers at this time,” a post shared to the Church’s instagram just before midnight on Monday.

“It is the Bishop and Father’s wishes that you also pray for the perpetrator.’’