Chairman of the Football Association David Bernstein has described recent incidents regarding fan behaviour as "disturbing".
The 69-year-old was speaking after yesterday's 3-2 win for Manchester United over Manchester City at the Etihad Stadium, where defender Rio Ferdinand was hit just above the eye with an object thrown from the crowd.
"What happened is totally unacceptable and deplorable to see those incidents and see Rio Ferdinand with blood on his face is absolutely terrible," Bernstein told Sky Sports News.
"It's sad to see such a fantastic match followed by the headlines that we've seen this morning. I think it's disturbing that we're seeing a recurrence of these sorts of incidents. We've had some racial abuse issues, things being thrown at players. [It's] very unacceptable and they have to be dealt with severely."
The FA and the police are investigating yesterday's incident from the Manchester derby.