"They started having words with a group of men and then punches were exchanged. They chased one of the men onto the forecourt and he fell over.

"He was punched and kicked against the petrol pump. It was sickening the way he was attacked while lying unconscious.

"The attackers were Asian and black. I don't know if it was racially motivated or not. I have passed the footage onto the police who are investigating.

Detective Constable Sandra O'Reilly, from Birmingham's Violent Crime Team, said: "We are aware of CCTV that has been circulated that shows the ferocity of the attack.

"Two men have been arrested and bailed pending further enquiries and we are yet to trace a further two men who we believe were involved in the attack.

"We believe that someone will know the men and would appeal for them to come forward.

"Our enquiries continue and we would ask the men in the footage to do the right thing and hand themselves in; it is only a matter of time before we come knocking at your door.