The Russian billionaire did not attend Saturday's FA Cup final at Wembley when the Blues beat Manchester United 1-0.

A source close to the 51-year-old suggested he was in the process of renewing his visa, and said it was taking a little longer than usual.

Asked about the visa, Security Minister Ben Wallace said: "We do not routinely comment on individual cases."

Mr Abramovich's office said it does not discuss personal matters with the media.

Reports suggest his investor visa expired three weeks ago.

The delay comes amid increased diplomatic tensions between London and Moscow after the poisoning of former Russian spy Sergei Skripal in Salisbury.

BBC home affairs correspondent, Daniel Sandford said Mr Abramovich appears to be able to run his businesses in Russia without significant interference from the Kremlin, suggesting that he is reasonably close to President Vladimir Putin.

But he said it was not clear if the delay in renewing his visa is in any way linked to the deterioration in relations between the two countries.

Mr Abramovich, who made his fortune in oil and gas in the 1990s, became owner of the companies that control Chelsea in 2003.

According to the Sunday Times Rich List, he is Britain's 13th-richest man, with a net worth of £9.3bn.

He owns a mansion on Kensington Palace Gardens, the most expensive street in London.

Mr Abramovich is also the former governor of the remote Chukotka region in Russia's Far East.

He has been a regular visitor to the UK since buying Chelsea, attending many of the home matches, and has been to Wembley for previous cup finals.

His private Boeing 767 left the UK on 1 April. It has since travelled to Moscow, New York, Monaco and Switzerland but does not seem to have returned to Britain.

The 51-year-old is one of Russia's richest billionaires
He reportedly sold dolls before making his fortune in oil during the perestroika years in the 1990s
Mr Abramovich was a one-time business partner of the late tycoon Boris Berezovky, an associate of former Russian President Boris Yeltsin
Critics say the two businessmen used their Kremlin "family" ties to acquire key state companies for below market value
Abramovich served as governor of Russia's Chukotka region
He is believed to be close to current Russian President Vladimir Putin