The alleged altercation is said to have occurred after the Alright rockers performed at the Beachcomber holiday park in Cleethorpes, England, as they tried to invite their guests back to their dressing room.

O'Neill has posted a picture on Instagram.com showing himself with nasty facial injuries, and alleged he was hurt in a brawl involving security guards.

"Here's the results of the vicious beating I took... at Cleethorpes Beachcomber on Saturday night, all because I was merely trying to get my guests back into the dressing room to get some items signed," the musician wrote in a post on the photo-sharing site.

He later took to Twitter.com to assure fans he was not badly injured.

"I'm fine thanks folks, just pretty shaken after what was frankly a vicious attack," O'Neill tweeted.

The holiday park's director, Richard Varley, has confirmed an investigation into the incident is underway.

"Following the regrettable incident at the Beachcomber on Saturday night following a very successful gig, an incident involving Keith O'Neill of Cast took place," Varley tells Britain's Liverpool Echo newspaper.

"We are urgently carrying out a full investigation into what happened. We would like to stress that this process will take some time to complete properly, in the meantime our contracted security firm have been suspended until further notice."

A representative for Humberside Police confirmed to the paper that officers attended an incident at the park on Saturday evening, but they have received no official complaints.