Police say one man has been arrested and he is helping them with their inquiries.

The attack occurred at Christ The Good Shepherd Church in Wakeley.

Graphic video uploaded to social media on Monday night shows Bishop Mar Mari Emmanuel standing at the altar of the church and speaking to parishioners as a man wearing a black jumper walks towards him and pulls out an implement.

As horrified churchgoers scream, the man stabs the priest in the chest. The priest then falls to the floor and is stabbed a further five times as a group of churchgoers rush towards him and manage to separate the alleged assailant from the priest.

Video taken in the aftermath of the stabbing show the bishop on the floor with as parishioners hold bandages against his head.

The episode was livestreamed.

Four people were injured in the attack - a man in his fifties was taken to Liverpool Hospital with multiple lacerations, as was a man in his thirties.

NSW Ambulance were treating a man in his twenties with lacerations to his hand and a man in his sixties with lacerations to his arm at the scene on Monday evening.

MNA/PR