Newcastle United fans have been warned by police not to taunt Paolo Di Canio, the manager of fierce rivals Sunderland, with fascist salutes.
Ahead of Sunday's Tyne-Wear derby, Steve Neill, of Northumbria Police, said: "Offensive gestures, particularly those with a suggestion of racist connotations, are completely unacceptable and we will take positive action against anyone seen acting in an offensive or racist manner.
"While some individuals may see this sort of behaviour as a means of poking fun at opposing fans - it is not a joke."
"Offensive behaviour can constitute a criminal offence and such behaviour is taken seriously."
"Football matches are routinely monitored by CCTV and even if action is not taken during the match, it can be checked retrospectively."