New York City police are hunting for thieves who burst into a Brooklyn church and brazenly stripped a bishop of the jewellery he was wearing while he was delivering his Sunday sermon as the service was livestreamed, officials said.

Bishop Lamor Whitehead of the Leaders of Tomorrow International Ministries was on stage when at least two men wearing dark clothing and face coverings entered the sanctuary, a video obtained by ABC affiliate WABC shows.

The thieves, who were brandishing at least one gun, can be seen walking up to the bishop, who promptly lies on ground.

The robbers then appear to remove various items of jewellery from him before fleeing. It was unclear how many people were in the church at the time of the robbery.

The bishop said in a video posted on Instagram that the robbers drove away in a white Mercedes.

New York City Mayor Eric Adams has vowed to hunt down the thieves.

"No one in this city should be the victim of armed robbery, let alone our faith leaders and congregants worshiping in a house of God," Mr Adams told the New York Daily News.

During a Facebook live yesterday, Bishop Whitehead offered a $50,000 cash reward to anyone who had information that would help the police investigation.

"Y'all don't get to do that to my family and get away with it," he said.

The bishop said the men took "hundreds of thousands of dollars worth of jewellery".

A spokesperson for the New York City Police Department told Reuters that the value of the jewellery taken was not immediately available.

Police said investigators are interviewing witnesses and reviewing video footage.

"My church is hurting," Bishop Whitehead said.