The World Chess Federation (Fide) says it has had its Swiss bank accounts closed over accusations its president facilitated business deals for the regime of Syria's Bashar al-Assad.

Kirsan Ilyumzhinov, a Russian multimillionaire and politician, was added to a US Treasury Department sanctions list in 2015 for allegedly “materially assisting and acting for or on behalf of the government of Syria“.

Of the four individuals on the sanctions list, one was accused of serving as a middleman for the Syrian government to purchase oil from Isis. The group was accused of "enabling Assad to continue inflicting violence on the Syrian people".

Mr Ilyumzhinov has repeatedly denied the allegations and withdrew from Fide while he sought to clear his name.

However, a letter from Fide’s treasurer said: “Since then Kirsan Ilyumzhinov has unsuccessfully tried several times to be removed from this list and at the moment there is no hint at all that there will be a change.”

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In the letter, Adrian Siegal said Fide was facing a “serious problem” and Swiss bank UBS had closed its bank accounts due to Mr Ilyumzhinov being on the sanctions list.

“After more than two years of Kirsan Ilyumzhinov’s presence on the sanction list of the US Department of the Treasury the Swiss bank UBS has announced that they will immediately close our accounts,” the letter said.

It added: “In summary, Kirsan Ilyumzhinov’s problems severely damage Fide’s business activities and we have to look for a new bank connection. In the process of this change we anticipate some problems.”

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Mr Ilyumzhinov has denied the accusations, and Interfax news agency quoted him as saying the bank accounts were not blocked.

"No one has blocked the UBS accounts, they are all active, I have checked recently. All events are taking place," he was quoted as saying.

UBS said it could not comment on whether individuals or organisations were clients of the bank.

Mr Ilyumzhinov is still listed as the federation’s president on its website. David Kramaley, founder of chess learning site Chessable.com, said: “This kind of turmoil at the top of chess has got to stop for the good of the game. The game needs stable leadership.”

President of the governing body since 1995, Mr Ilyumzhinov was also president of the Russian Republic of Kalmykia from 1993 to 2010.