Witnesses have described how two sets of football fans created a “mini riot” in Watford town centre.

Stunned shoppers and traders watched in horror as more than 100 rival Manchester City and Manchester United fans clashed before Saturday’s FA Cup semi-final at Wembley.

Drunken supporters hurled bottles, chairs, glasses and ashtrays at each other as passions spilled out of control.

Witnesses claimed that a large group of more than 100 Manchester City supporters traded blows with a smaller group of Manchester United fans outside The Columbia Press bar before chasing them down The Parade.

The remaining supporters are then said to have hurled foulmouthed abuse at passers by and intimidated shoppers with rowdy singing well into the afternoon.

John Stevenson, who was working on a fruit and vegetable stall close to the fracas, said: “There was a group of Manchester united fans drinking outside the Columbia Press. At about 10.20am a bigger group of Manchester City fans came around the corner. There was about 50 of them. They saw the Manchester United fans and charged at them.

“Punches were thrown and they threw chairs and bottles at each other. It really was like a mini riot out there. I’ve been going to football matches for 35 years and it was as bad as anything I’ve seen.”

Other witnesses explained how the situation calmed down once the Manchester United fans had been “chased” further down the High Street. It is believed that many of the fans had tickets for the game and were simply staying in town before catching the train to the stadium.

Dozens more fans, however, remained in town well into the evening to watch the game, which didn’t kick off until 5pm.

Martin Valentine, who also watched the situation unfold, added: “It was really bad. They were very intimidating; singing really loudly, swearing a lot and running down the town. People didn’t want to sit outside at the restaurants or go in the shops, which was a real shame.”

Rob Borghi, manager of the Zinco Italian restaurant, added: “I was upset because I lost a lot of businesses from it. People did not want to sit outside and eat because they felt intimidated.”

Hertfordshire Constabulary said it anticipated a large turnout of fans and responded accordingly.

A spokeswoman said: “We monitored the situation closely and altered our policing response as more information became available throughout the day, as we do with all intelligence surrounding football matches.

“Unfortunately two minor public order incidents occurred during the day on Saturday on the High Street which were dealt with. There were no injuries and no reports of assault following these incidents and no arrests were made. There were no further reports of unrest after the match on Saturday evening."