MOSCOW – Russia urged CSKA Moscow fans flying to London for this week's Arsenal match to exercise extreme caution due to Britain's "anti-Russian campaign".
Moscow and London have been waging a furious diplomatic war since the March 4 nerve agent attack on Sergei Skripal and his daughter in England.
Britain accuses Russia of poisoning the former double agent in retribution for passing on state secrets to London.
Moscow calls the allegations unsubstantiated anti-Russian propoganda.
The incident has sparked mass expulsions and a decision by Britain and some of its allies not to send officials to Russia's World Cup in June.
Russia's UK embassy on Sunday told CSKA fans to display "extra vigilance" when visiting London for Thursday's Europa League clash.
"Considering the anti-Russian campaign being waged by Britain, which has led to a rise in Russophobia, we call on you to exercise extra vigilance and discretion," the Russian embassy said.
"To avoid provocations, we call on you to avoid getting into conflicts with the authorities and local residents."
The embassy also encouraged supporters to "behave with our inherent dignity" and to keep track of their money and personal items.
The Moscow Red Army club and the Gunners have been drawn in the Europa League quarter final.
Russia's World Cup organiser took the unusual step last month of issuing a security guarantee to Arsenal faithful flying to Moscow for the April 12 second leg of the tie.
But relations appear to have actually deteriorated since.
Moscow accuses London of using fake evidence to convince more than two dozen European countries and the United States to kick out some of their Russian diplomats.
It also alleges that the entire crisis was part of London's orchestrated campaign to strip Russia of the June 14 to July 15 World Cup.
"I am getting the impression that they are ready to do anything to take the World Cup away from Russia," foreign ministry spokeswoman Maria Zakharova said on Saturday.
"They are ready to do it by any means possible. Everything is focused on that football that – God forbid – touches a Russian pitch."
Sunday's travel warning echoes one issued by the Foreign Office when it announced the expulsion of 23 Russians on March 14.
London also spelled out the risks of "anti-British sentiment of harassment" in Russia.
Thursday's game comes with anxieties already running high about Russian hooligans travelling to London.
A Basque policeman died of a heart attack during street battles between Spartak Moscow and Athletic Bilbao supporters ahead of another Europa League match in February.
The world football governing body FIFA expressed its "complete trust" in Russia's ability to ensure a safe World Cup after that violence.