Harry Potter star Josh Herdman caused havoc at a film convention in Copenhagen, Denmark - after drunkenly abusing fans and demanding an ambulance, according to U.K reports.

The actor, who plays bully Gregory Goyle in the wizard franchise, attended the Collectormania comic and film event last weekend and was expected to meet-and-greet fans.

But the star shocked Potter devotees after allegedly romping with a half-naked blonde and staggering around the convention swearing and shouting, reports Britain's The Sun newspaper.

A source tells the publication, "Herdman was an utter disgrace. He was out of his skull when he arrived and his behaviour got worse. Lots of kids came to see him. He was meant to meet them with a smile and sign autographs. But they were greeted by a scowling, offensive, foul-mouthed drunk."

The hotel guest adds, "He came into reception and started screaming abuse at Collectormania's organisers. At one point he screamed, 'I am a regular cast member in the biggest movie franchise in cinema history and you will not speak to me like that!' He kept kicking off in the hotel all evening.

"Staff tried to get him to check out but he started crying for an ambulance, saying he was going to die. He finally collapsed in the toilet with his trousers round his ankles. When staff tried to get him to move he started screaming and bolted into the cafe next door. Police and an ambulance were called because he was clearly out of control."

The newspaper claims that Herdman was seen to by paramedics, before cops ordered him to pay his bill and leave the venue. No arrests were made.