Police were called to break up a brawl outside Liquid and Envy nightclub
A student pub crawl descended into a mass "disturbance" involving about 300 people and leaving three injured, police said.
Three men were arrested after the fight broke out in Colchester in the early hours of Friday.
The disturbance followed a pub crawl organised by Rampage, which ended at Liquid and Envy nightclub at 03:00 BST.
A spokeswoman for Liquid and Envy said they "do not tolerate anti-social behaviour of any kind".
"Unfortunately, during a promoter-led event last night, there was an isolated incident outside the club. We will be working closely with the police to make sure that those involved are identified and appropriate action taken," she said.
'Disgraceful behaviour'
Police arrived on the scene shortly after the nightclub closed, and had to call in extra officers for back-up.
The three men arrested on suspicion of assault are aged 20, 21 and 23. They were taken to Colchester police station for questioning.
Three people suffered injuries and one man required hospital treatment after being knocked unconscious.
The Rampage event was advertised online as the biggest student organised pub crawl in the town. The BBC has been unable to contact Rampage.
Ch Insp Richard Melton said: "We will not allow Colchester or anywhere else in Essex to be used as a venue for such disgraceful behaviour.
"We responded quickly and effectively to quell this disorder and we will be taking further steps to identify the main people responsible and prevent any repeat events."
