Five years after the event that changed his life, Irish businessman Denis Sugrue, 58, claims that U.S. government still thinks he's a spy.

The ordeal began in 2005 when Sugrue's Ireland-bound flight was halted on the tarmac of the Los Angeles International Airport. Moments later four armed FBI agents came on board, waving an arrest warrant in his face and leading him away in handcuffs.

His offense, they told him, was being a Russian agent. For the Galway based businessman it was as if a bizarre joke was being played, but he soon discovered they weren't laughing. Even at home in Galway his friends and neighbors were mystified by the arrest.

What Sugrue didn't know he was that for days he had been carefully monitored by U.S. counterintelligence agents who had been following him in cars and staking out the airport. What he could not imagine was that he was about to be detained in US custody for 15 weeks.

Five years after his ordeal Sugrue has just published a memoir about the events that changed his life. And to this day he insists that, despite never having been charged with any offence, the U.S. government still believes they got the right man.

'They still think that I'm a spy,' he told the Irish press from Russia, where he is based with his family and from where he runs his technology company Amideon.

As he admits himself, Sugrue certainly fitted the kind of profile the authorities might take a second look at: he was a travelling businessman dealing in high-end technology with resident addresses in Ireland, Moscow and Kyrgyzstan. It sounded like a page from an espionage novel.

When he was targeted in the U.S. for purchasing a electronic device known as an 'equalizer/demodulator' for shipping to Russia via Limerick, he was, he insists, simply shipping standard broadcasting equipment designed and sold with official consent.

'We had a deal with an American company to co-design a product for the equivalent of the Federal Communications Commission (FCC) in Russia,' he explained.

But the F.B.I. weren't buying it, at least not at first. 'I was thrown in prison and the case began to unravel because the thing that we were buying was legal to buy and we had all the supporting documents,' he said.

'But for some reason Time magazine ran an article which was called 'The Russians Are Coming' and it said I was part of a Russian spy ring in America. Newsweek said later that the FBI called it a major breakthrough in curbing Russian espionage.'

Sugrue believes the operation was at least partly motivated by the political climate of the day. There was, he claims, pressure on President Bush to be seen to tackle the perception that Russia was flooding the U.S. with spies.

'I was detained for 15 weeks. It was a combination of prison (the Metropolitan Detention Centre in Los Angeles) and I was electronically tagged all the time. Then I was on a 30-metre electronic chain so I couldn't move. That was outside prison in the house of a friend of mine,' he said.

'I think they genuinely thought that they had a spy – a guy spending 15 years in Russia and doing business in Russia. They were looking for someone.'

Sugrue has spent the past few years writing his memories of the affair in his newly published book The Russians Are Coming. He hasn't returned to the U.S. during those five years but he does still continue to trade with his American business associates. He is, he says, free to come and go as he pleases but America will never seem as hospitable is it may once have been.

'I believe they are still watching me,' he said. 'That is what they said so I have to believe them. But they can if they want to.'