The Russian Foreign Ministry has said the United States detained one of their citizens a day after Moscow arrested American Paul Whelan on suspicion of spying.

Dmitry Makarenko was held on December 29, just 24 hours after Marine veteran Paul Nicholas Whelan, 48, was arrested accused of participating in a 'spy mission'.

Makarenko was accused in June 2017 by federal prosecutors of conspiring to export defense articles from America to Russia without US approval.

He was detained by the FBI on the Northern Mariana Islands, a US commonwealth in the Pacific Ocean, and transferred to Florida.

The ministry said: 'Makarenko, born in 1979, has arrived on Saipan Island with his wife, underage children and elderly parents. He was detained by FBI personnel at the airport right after his arrival.'

Marine veteran Paul Nicholas Whelan, 48, was arrested in Russia on December 28

The ministry said the United States detained Russian citizen Dmitry Makarenko on Dec. 29 on the Northern Mariana Islands, a U.S. commonwealth in the Pacific Ocean

Makarenko was accused, along with Vladimir Nevidomy, pictured, of conspiring to export defense articles including night-vision scopes from America to Russia without US approval

Papers filed in Florida show Makarenko was accused, along with Vladimir Nevidomy, of conspiring to export defense articles including night-vision scopes.

He was declared a fugitive in January 2018.

Nevidomy, of Hallandale Beach, Florida, pleaded guilty in June 2018 and he was sentenced to 26 months in prison, the court papers showed.

Whelan was taken into custody by Russia's Federal Security Service on December 28 but his family protested his innocence, saying he was in Moscow for a wedding.

The accusations from both sides could further complicate a strained relationship between Moscow and Washington.

U.S. Secretary of State Mike Pompeo has already asked Moscow to explain Whelan's arrest and would demand his immediate return if it determined his detention is inappropriate.

The Russian ministry said in its statement that Moscow diplomats had not been able to reach Makarenko in Florida and said Washington had yet to explain his detention.

Experts had speculated Whelan is being held as leverage for the return of Russian Maria Butina.

The U.S. Embassy in Moscow could not immediately be reached for comment. A State Department spokesman in Washington referred a request for comment to the Department of Justice, which did not immediately respond.

Marine veteran Paul Nicholas Whelan, 48, was arrested in Russia on December 28

Experts have speculated Whelan is being held as leverage for the return of Russian Maria Butina and US Secretary of State Mike Pompeo has asked Moscow to explain his arrest

It comes as Twitter sleuths have started to question the wedding alibi of Whelan after no evidence of the marriage emerged.

His twin brother David insisted he was visiting Russia for the marriage of an old Marine Corps buddy.

But online people have questioned why there are no pictures from the wedding or any more details about the couple.

One wrote: 'Who is the US marine that got married in Russia? Paul Whelan, the man arrested for espionage by Russia was supposedly there to attend a wedding.'

Another added: 'This is getting weirder by the minute. Canadian/Irish/US citizen ex-marine Trumper, discharged for stealing, works in car parts manufacturing, went to Russia for a wedding (is the wedding still on?) arrested by Putin for being a spy. Who knew car parts were national security.'

And one questioned: 'Who was this blissful wedding couple?'

Paul was said to have arrived in Russia on December 22 for the wedding of friend and a Russian woman the following Friday.

He spent the day of the marriage, December 28, with bride and groom at the Kremlin, according to David.

But when he didn't arrive at the wedding later that day David says the couple reported him as missing, CNN reports.

TIMELINE OF PAUL WHELAN'S ARREST December 22: Paul Whelan travels to Russia for a friend's wedding December 28: Whelan spends the day with the bride and groom at the Kremlin acting as a tour guide He does not attend the wedding later that day and the couple file a missing-person report with Russian authorities December 31: Whelan's family learn about Paul's detention after media reports emerged January 4: David Whelan appeals to the US government to pressure Russia to release him and say he is completely innocent January 5: The Russian Foreign Ministry says the US detained a Russian citizen, a day after Moscow arrested Whelan on suspicion of spying Advertisement

One Twitter user commented: 'They would definitely know wouldn't they. In every film I've ever seen the family have no idea at all that their husband/father is a spy. ITS A SECRET - THAT HOW SPYING WORKS.'

Another added: 'This man has all kinds of connections in Russia. No one has said whose wedding he was attending. Sketchy details.'

Speaking to the Dailymail.com his brother David said: 'Paul did not attend the wedding. That is what caused concern. The groomsman was his former Marine friend, the reason Paul went to Moscow. It was totally out of character for Paul to have missed the wedding after having spent part of the day with the wedding party on a sightseeing tour.

'We have spoken to the friend since Paul's detention and he made a report of Paul being missing to the U.S. Embassy before the Russian government issued its news release on Monday. Paul was detained at some time before the wedding on Friday night.

'We are not making the friend's name public at his request, for privacy and personal security reasons.

'His friend tried to contact us that weekend and made the report on Sunday. Like many people, Paul's friends don't necessarily know Paul's other family or parents. As soon as we contacted the Embassy on Monday, they were very helpful in sharing what they knew, which wasn't much and remains without details from the Russian government.'

Twitter sleuths have begun to question the US Marine 'spy's' Moscow wedding alibi

The couple getting married are said to have reported Paul missing when he didn't show up

Whelan also has passports for the UK, Ireland and Canada, where he was born

Paul's brother David Whelan appeared on CNN on Tuesday to proclaim his brother's innocence

David Whelan described his brother Paul as 'very loyal to family and friends'

Whelan is believed to have been arrested in the Metropol Hotel in possession of a flash drive with a list of Russian government employees.

It has also emerged that in addition to being a U.S. citizen, Whelan has passports for Canada, the UK and Ireland.

In a Washington Post op-ed published Friday, David urged the U.S. government to pressure Russia to release him.

'Paul is a kind and considerate brother, son and uncle, and a generous and loyal friend,' he wrote. 'He travels as often as he can, both for work and pleasure. He is many things to many people, but he is not a spy.'

Whelan could face up to 20 years in prison if convicted of spying.

His is being held in Lefortovo, a notorious prison run by the KGB in Soviet times and still used for foreigners accused of spying.

Further details of Whelan's past have also emerged, showing he has a pattern of exaggerating his experience in law enforcement.

Whelan was dishonorably discharged from the Marines and exaggerated cop credentials

He friends with Russians with military connections on social media site VK

Whelan claimed in a 2013 deposition that he was a former sheriff's deputy in in Wash­tenaw County and a police officer for the city of Chelsea.

Wash­tenaw County told the Post that they had no record of Whelan's employement, and Chelsea police records show that he worked as a 'part-time police officer, as well as a dispatcher, a crossing guard, and a parking officer.'

Former CIA officers have expressed doubts that Whelan was working for U.S. intelligence. They note that the CIA would be unlikely to use someone in Russia without diplomatic immunity and leave them vulnerable to arrest.

Whelan's Marine record also would likely prevent U.S. intelligence from hiring him.

He began active duty with the Marines in 2003 and was deployed twice to Iraq, rising to staff sergeant. But his military career ended with a court martial in 2008, when he was convicted on charges that included attempted larceny and dereliction of duty.

Court documents released by the military show he was accused of attempting to steal more than $10,000 while on duty in Iraq, where he worked as a clerk, in September 2006. He was also convicted of using a false social security number and profile for a military computer system to grade his own examinations, and of writing 10 bad checks totaling around $6,000.

He was dropped two grades in rank and given a bad conduct discharge from the Marine Corps.

After his discharge, Whelan returned to his job in the temporary staffing company Kelly Services, based in Troy, Michigan, where he had worked since 2001 in the IT department until taking the leave of military absence. He was Kelly's head of global security and investigations until 2016.

Early the following year, Whelan joined auto parts supplier BorgWarner as global security director, focused on physical security of company property. BorgWarner, based in Auburn Hills, Michigan, has facilities around the world but none in Russia and he never traveled to the country for business, company spokeswoman Kathy Graham said.

Whelan (above) exaggerated his experience as a crossing guard to claim he had law enforcement experience, and was dishonorably discharged from the Marines

Whelan appears to have spent a decade cultivating contacts among Russian security personnel.

Whelan has been visiting Russia since at least 2007, when he took advantage of a military program for Marines deployed in Iraq that gave them 15 days of leave and paid for the travel.

'Having grown up during the Cold War, it was a dream of mine to visit Russia and meet some of the sneaky Russians who had kept the western world at bay for so long!!' he wrote of his first trip to the country on his now-defunct personal website.

Even before the trip, he had begun developing a network of contacts throughout Russia. Some said they met him online in 2006 and became 'pen pals,' trading practice in English for Russian. Whelan seemed fascinated with Russia and its culture, they said.

For nearly a decade, he has had an account on VKontakte, the Russian version of Facebook which translates as In Contact.