A suspected Isil terrorist could be blocked from returning to Ireland if it is proved he lied to immigration officials to get citizenship.

Alexandr Ruzmatovich Bekmirzaev (45), originally from Belarus, left Ireland in 2013 to travel to Syria.

He was captured by Kurdish fighters battling against the jihadists at the end of last year.

Now gardaí, who described him as "a serious player" after he was captured in Syria, are investigating his immigration status.

Their inquiries could lead to his citizenship and his passport being revoked and him being banned from entry when he is released.

Mr Bekmirzaev, who lived here for 13 years before going to Syria, was believed by Garda anti-terrorist officers and military intelligence to be a key member of a logistics support cell for Isil in Dublin.

He is now under investigation by the Garda national immigration bureau. As part of his citizenship application, he claimed he was legally married. But it has since been alleged that his marriage was a sham and he paid a woman to marry him.

Immigration officers are working closely with the Irish Naturalisation and Immigration Service to determine his status when he lodged his application.

If it is found that he deceived the authorities here, Ireland would be under no obligation to accept him back whenever the Kurds decide to release him from their custody.

Mr Bekmirzaev arrived in Dublin in 2000 and did not become known to gardaí for the following decade.

He did not come through the asylum system and had work permits allowing him to obtain jobs, mainly in the fast food business in the city centre. He also worked at times as a security guard.

He and his family did not have any permanent address but lived in several short-term lets.

He became an Irish citizen, taking part in a formal ceremony, in 2010.

Shortly after that, he is said to have come under the influence of an active Isil supporter, a Jordanian believed by the Garda to be the key recruiter for the jihadists in this country.

The Jordanian was eventually deported.

In the meantime, Bekmirzaev and some others had been radicalised and became part of a logistics cell, supplying back-up assistance, helping with travel plans and fund-raising as well as providing documentation.

Gardaí said Mr Bekmirzaev, who travelled to Syria via Istanbul, was one of at least 30 people with Irish passports known to have flown out to Isil's so-called caliphate in Syria and Iraq from Ireland.

Some were backing Isil while others sided with the Kurds.

Most of them are now believed to be dead.

Mr Bekmirzaev was one of half-a-dozen Irish passport holders believed to be still operating on behalf of Isil in Syria until his capture by the Kurd-led Syrian Democratic Forces (SDF) on December 30.

He has always denied he was a fighter.

In an interview with the London 'Independent' in February, he maintained he went to Syria to help Muslims but was forced to work as a driver for foreign fighters in the area around Raqqa.

Irish Independent