Three bars on Brighton's Palace Pier were shut by police after an officer was injured breaking up a stag party brawl.

The policeman is believed to have been hit in the face with a glass or bottle during the fight which broke out in Horatio's karaoke bar at about 8.30pm on Saturday.

Horatio's, the adjacent Offshore Bar and the Victoria Bar were all closed, although the Victoria was allowed to reopen an hour later.

The other two remained shut until yesterday.

Another Brighton seafront bar, Kruze, was also cordoned off by police following an incident believed to have involved a stag party.

The night of violence came as tourism leaders warned levels of drunken disorder and late-night crime in the city could threaten its £382 million tourism industry.

The Brighton and Hove Tourism Strategy says disorder on the streets could scare off big-spending visitors and highlights the popularity of the city for stag and hen nights as a problem.

Witnesses say more than one stag party was in Horatio's when the violence broke out.

One man, a regular at the bar for more than ten years, said: "It was absolutely packed at the time. It seemed to start with a stag party from Kent but there was more than one stag party in there. They were just a bit unruly, too much alcohol, really. Fighting started and tables were overturned. The security guards saved a lot of people from being injured and the police were there within minutes."

He said officers used pepper spray to control some people involved in the trouble.

He added: "I jumped behind the bar with one of the girls. Everything was going everywhere and then it spilled outside."

The injured officer was taken to the Royal Sussex County Hospital and Sussex Ambulance Service said another person refused treatment.

Charles Quelch, general manager of the Palace Pier, described the incident as minor.

He said: "The trouble was isolated. From our reports, the police were in control from the start. We were very busy on a sunny, summer Saturday."

Earlier, a brawl broke out at the Kruze bar which is believed to have involved another stag party.

Kruze owner Allan Love described how about 30 men started fighting after an argument started at about 4pm.

No one was seriously injured and police were on the scene within minutes. The bar was shut for about three hours.

Mr Love said: "I didn't see how it started because I was upstairs in the kitchen but it was a bit of a surprise because it kicked off so early in the day.

"I don't think any of them were drunk and when the police arrived and it calmed down some of the guys from both sides of the fight came over to apologise."

At the time of the later trouble on the pier, hundreds were on the seafront nearby watching a 25th anniversary outdoor screening of Quadrophenia, the film set during the clashes between Mods and Rockers on Brighton beach in the Sixties.

Liberal Democrat leader on Brighton and Hove City Council Coun Paul Elgood warned groups of drunken men could intimidate other visitors.

He said: "Traditional stag weekend venues such as Dublin are trying to shed that image and seek another direction.

"Brighton and Hove does not want to become known as the new stag venue.

"If stag nights lead to more drunken behaviour, police need to be looking more closely at this."

Six men from the London area were arrested and are being questioned by police about the violence on the pier.