Detectives want to find Jack Costello, 45, pictured, after a 23-year-old man was seriously assaulted in Esco-bar, in The Green, Drawen, around 1.20am today.
The 23-year-old man was taken to Royal Preston Hospital for treatment but sadly died this morning.
Lancashire Police says it is keen to trace Costello in connection with the investigation.
He is described as white, 5ft 10in tall, of stocky build, with short cropped hair. He also has a lazy eye.
Detectives are appealing for information and urging anyone who has seen him or knows where he is not to approach him, but instead contact police.
Det Supt Simon Giles, of Lancashire Police’s Force Major Investigation Team, said: “Jack Costello is wanted in connection with an extremely serious offence.
“He is a potentially dangerous and violent individual. If you see him, do not approach him. Instead contact police immediately.
“Anyone with information can contact police on 101 quoting log reference 0958 of January 28.”