Moscow: Russia has issued a security guarantee to Arsenal fans who will visit Moscow for a Europa League clash in the heat of a diplomatic crisis over an ex-double agent’s poisoning.

Moscow on Saturday announced the expulsion of 23 British diplomats in a tit-for-tat response to London’s “provocative” measures over the nerve agent attack on Sergei Skripal and his daughter in England.

Britain issued a travel warning to people in or planning to travel to Russia after expelling the same number of Moscow diplomats on Wednesday.

And Foreign Secretary Boris Johnson on Friday said it was “overwhelmingly likely” that Russian President Vladimir Putin personally ordered the attack.

The Kremlin called his comments “shocking and unforgivable”.

All of which has left Arsenal fans alarmed about the prospects of playing CSKA in Moscow on April 12 for the second leg of their Europa League quarter-final.

One Arsenal supporters’ group called it “a hot potato of a draw in view of the political stand-off”.

The club itself reposted on its website a Foreign Office travel advisory warning of possible “anti-British sentiment or harassment”.

Russia’s World Cup organising committee chief Alexei Sorokin expressed disappointment about the tensions and said Arsenal fans have nothing to fear.

“It is a shame that the games will be played in such circumstance,” said Sorokin, who is also a senior member of the Russian Football Union.

“We will ensure security in equal measures to all — from dignitaries to fans,” Sorokin said.

But he also expressed a hint of annoyance at Arsenal’s decision to put up the Foreign Office travel advisory after Friday’s Europa League draw.

“To us, there is no difference which country people come from or what our diplomatic relations with them are,” he said.

“There are absolutely no grounds for such warnings.”

Sorokin has been fighting an uphill battle to clean up Russia’s image ahead of its first World Cup at home, starting on June 14.