Manchester United have advised their fans heading to Rostov this week not to wear the club's colours while in the Russian city.
Jose Mourinho's United face FC Rostov on Thursday night in the first leg of their Europa League last-16 tie.
There are concerns about the safety of supporters going over for the game, with English and Russian fans having clashed in violent scenes during the Euro 2016 finals in France last summer.
According to the Telegraph, United's head of ticketing and membership Sam Kelleher has sent a letter to fans travelling to Rostov regarding the issue.
It says: "For your safety and security you are advised not to wear Manchester United colours when in Rostov, or attract attention to you presence in the city.
"It is also advised you stay in groups where possible and do not walk around the city alone. It is not just opposition football fans who may potentially pose a risk to your safety.
"Incidents of serious disorder during the European Championships in France last summer, involving violent individuals and groups emanating from Eastern Europe, should be remembered when considering your movements and actions and any potential risk."
It is not the first time this season supporters of an English club have been advised not to openly display their club's colours while in Russia.
Tottenham's followers were also warned against wearing club shirts when they were in Moscow for a Champions League game against CSKA in September.
Back then, a statement from the London club read: "Please note, for additional personal security, it is suggested you do not show your football colours until you are inside the stadium.
"Whilst flags and banners are welcome at the stadium, we recommend that they are not openly shown in the city centre."