A Shomrim volunteer was "viciously assaulted" in Stamford Hill in what the strictly Orthodox neighbourhood watch group says the first attack ever against a volunteer.
The man, who is believed to be in his twenties, was hospitalised after suffering injuries to his face while he was responding to a call about criminal damage on Tuesday evening.
Shomrim shared a close-up photo of the victim that showed him with a bloodied eye.
Chaim Hochhauser, a volunteer for Shomrim, said the incident was the first attack against a volunteer since the group was established in 2008.