Earlier, UK officials told The Times newspaper that Paul Whelan, who was detained in Moscow last Friday on suspicion of espionage, holds British citizenship.

London has confirmed that Paul Whelan is a UK national and requested consular access to see him, a Russian Foreign Ministry spokesman told Sputnik on Friday.

"He has British citizenship," the spokesman said. "The British side has made a request for consular access. It is being processed," he added.

Earlier, UK media reported that Whelan, a 48-year-old US national and ex-marine, was also a British national. This followed reports by Canadian media that Whelan was born in Canada and may therefore also retain a Canadian citizenship.

The UK's Embassy in Russia confirmed to Russian media that Whelan has requested the British diplomatic mission for help. Embassy employees "requested consular access to a Briton detained in Russia after receiving a request for help from him," the Embassy said in a statement.

Also Friday, British Foreign Secretary Jeremy Hunt expressed London's concern over the detained Brit's fate. "We are extremely worried about Paul Whelan, we have offered consular assistance," Hunt said, according to Reuters. "The US are leading on this because he is a British and American citizen," he added.

Whelan, who is officially employed as director of global security for a Michigan-based automotive parts supplier, was detained in Moscow on December 28, with Russia's Federal Security Service filing a criminal case against under the article "espionage." Alleging that Whelan had been detained "during a spy action in Moscow," the FSB offered few other details on the case. If convicted, Whelan may be sentenced to up to 20 years in prison. The US State Department was granted consular access to Whelan earlier this week.

On Tuesday, Whelan's twin brother David Whelan told CNN that his brother was innocent, and that he had traveled to Russia to attend a wedding ceremony. Further media investigation has revealed that Paul Whelan was a retired marine who had served serveral tours in Iraq, and that he was demoted and discharged from the military in 2008 after being court martialed on several counts of larceny. On Friday, a spokesperson for Whelan's former employer of 15 years told Sputnik that he had never traveled to Russia on official company business.