A man has been arrested after a police officer suffered a broken eye socket and nose in a protest by football fans outside Manchester United's ground.
About 1,000 protesters gathered at Old Trafford and 200 outside the Lowry Hotel in Salford before United were due to play Liverpool on 2 May.
Greater Manchester Police (GMP) said several officers were hurt during the protests.
A man, 25, has been arrested on suspicion of grievous bodily harm.
He is also being held on suspicion of violent disorder and burglary.
GMP said the officer suffered a broken eye socket, broken nose and a slash to the face when an object was thrown at his face at the Old Trafford protest.
Fans had gathered outside the ground and the hotel, where the team was staying before the Premier League game, to protest against the Glazer family's ownership of the club.
The game against Liverpool then had to be postponed after about 200 fans entered the ground.
GMP has appealed for anyone with information or footage of the demonstrations to contact the force.
"We are aware of multiple people having filmed the disorder so we urge anyone with footage that is of good quality to upload it the major incident portal or get in touch as a matter of urgency," Supt Caroline Hemingway said.