As a professional provocateur and vocal supporter of the war in Iraq, Christopher Hitchens has been engaged in countless verbal punch-ups with his ideological opponents, most of them conducted from the safety of a TV studio.

However, when the controversial author, journalist and broadcaster defaced a political poster on a visit to Beirut last week, he found himself at the wrong end of a bruising encounter that has left him walking with a limp and nursing cuts and bruises.

Hitchens had been drinking on Beirut's main boulevard, Hamra Street, on Saturday afternoon with two other western journalists after attending a rally to commemorate the assassination of the former Lebanese prime minister, Rafik Hariri. They spotted a poster for the Syrian Social Nationalist Party, a far-right group whose logo bears an uncanny resemblance to the Nazi swastika, and Hitchens decided to act.

"They would be better off calling themselves the Syrian National Socialist party, and that's what they are", he said, speaking to MediaGuardian.co.uk today after arriving in the UK by plane. "I couldn't tear it down but I got my marker out and wrote on it, effectively telling them to 'fuck off'."

Hitchens' political statement was witnessed by a group of SSNP activists, who have a strong presence in Beirut. "With amazing speed, in broad daylight on this fashionable street, these guys appeared from nowhere, grabbed me by the collar and said: 'You're coming with us'. I said: 'No I'm not'. They kept on coming. About six or seven at first with more on the way," he said.

He described how he was knocked to the floor, ended up with his shirt covered with blood after he cut his arm in the fall, and "skinned" two fingers on one hand. Hitchens added that he was walking with a limp for several days after. "They were after me because I was the one who had defaced the poster," he said.

After scrambling to his feet and "picking up my glasses and my notebook", Hitchens and his companions flagged down a taxi, but a member of the gang who had assailed him jumped in and they climbed back out on to the street, escaping to the safety of a busy coffee shop. A crowd confronted their assailants and the three men managed to escape.

The journalists then caught another taxi to a waterfront hotel "to throw them off the scent in case we were followed", although not before Hitchens had "taken a punch to the face through the car window". They returned to their own hotel later that afternoon.

Hitchens said he had been shaken by the attack. "I've just got off a flight. What shook me is how nearly it could have got fantastically nasty. We could have been hurt or taken away. These militias have their own private dungeons. I wouldn't fancy spending time in one of those."

He stayed on in Beirut to deliver a scheduled talk at the American University yesterday evening, where he was confronted by another group of SSNP members. "By that time they had worked out who I was and where I was going to be," he said. "So I took along some very nice comrades from the Popular Socialist Party to sit near me. [The rival activists] were outnumbered."

Hitchens added that his hosts had offered to take him to hospital but he had refused. "I'm too old to take chances. If you get kicked in the head or the stomach you should get yourself checked out but I didn't get a blow to my head or anything."

He is recovering in London today before flying back to his Washington home tomorrow and insists he is bloodied but unbowed. "It was a scrape. It wasn't 'honours even' but it wasn't a rout."

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