Dozens of police officers were injured during violence at a sectarian interface in Belfast, police said.
They were pelted with bricks, bolts and bottles after preventing loyalists from marching from the unionist Woodvale area towards the nationalist Ardoyne area.
One officer required 12 stitches to a finger after being bitten.
Water cannons were deployed to quell unrest, which broke out at the end of a largely peaceful Twelfth of July Orange Order commemoration.