An alleged Islamic State (IS) fighter arrested in Syria two weeks ago fraudulently gained Irish citizenship by marrying a British woman in a €3,000 sham marriage.

The 36-year-old ex-wife of Alexandr Ruzmatovich Bekmirzaev confessed that her nine-year marriage to the Bela- rusian was a complete sham, describing it as "a very stupid, childish thing I did".

The woman married Bekmirzaev in 2001 when she was a 17-year-old waitress living in Dublin away from her family.

"He gave me €3,000, but I literally believed I was stopping someone from being sent back to a country where they would be killed," she said.

"There was never romance, he wasn't my type, but he was my friend and I needed friends because I found it hard to make friends when I was living in Dublin.

"He really needed help and I did what I thought was the right thing at the time."

Bekmirzaev, who had registered ownership of a grocery store on Talbot Street, was captured by Kurdish-led forces in Syria in recent weeks.

The Syrian Democratic Forces said he and his alleged fellow IS fighters were preparing to attack civilians when they were captured.

Idiot

The revelations that Bekmirzaev's citizenship was based on a lie comes after Taoiseach Leo Varadkar vowed that, as an Irish citizen, he would be entitled to consular assistance.

The woman, who remained on good terms with Bekmirzaev for more than a decade, said she was "genuinely shocked" at news of his suspected involvement.

"I can't believe he got himself wrapped up in that. What an idiot," she said.

The woman was introduced to Bekmirzaev by a doorman at a pub where she worked shortly before they registered their marriage in January 2001.

"I was only 17, but I had studied Russian in school for five or six years. A doorman in a pub off Grafton Street, where I worked, introduced us," she said.

"To be honest, I thought about this for years afterwards, and I think they had that intention for us to marry from the beginning.

"I think it was just the fact I had a British passport, I was on my own and I was young and vulnerable and that's why he befriended me.

"The marriage was a very stupid and childish thing I did, but I literally believed I was stopping someone from being sent back to a country where they would be killed.

"It was something afterwards I very much regretted doing.

"I just think I was really stupid and very naive, and I regretted it."

It is understood that although Bekmirzaev applied for asylum after arriving in Ireland in 2000, he withdrew this application and was granted residency status after he married the woman in January 2001.

Remaining in Ireland and claiming more than five years of reckonable residence and marriage to an EU citizen, he was granted citizenship in 2010.