A would-be car thief who knocked himself out trying to break into a Mercedes has become an international laughing stock after video footage of the botched robbery went viral.

More than two million people have watched the CCTV images of the attacker in Ireland unsuccessfully throwing a stone at the car window outside an Irish pub.

When he fails to smash the screen he walks off before returning with what appears to be a concrete block which he launches at the luxury coupe.

But in a split second the makeshift missile rebounds, striking him in the head and knocking him dazed to the ground.

Gerry Brady, owner of the car and The Pheasant pub in Drogheda, Co Louth, said he found the man lying "completely dazed" beside the Mercedes after he finished work.

"He was lying on the road, I asked him 'are you ok mate?', as you do," he said.

"There was a lot of blood, he couldn't stand up. He was completely dazed.

"But he started saying his friend jumped on him and beat him up. My girlfriend was with me and she phoned the guards (Irish police) and ambulance.

"When I told him the guards were on the way, he was saying to me 'no guards, no police', so I knew something was up.

"Then I looked at my car and there were some divots taken out of the window and a concrete block on the ground.

"The penny started to drop at this stage."

Mr Brady said his girlfriend checked her own car nearby and it had been broken into, with an iPad and phone missing.

The items were later recovered.

The pair ran to a nearby filling station where they hid until the emergency services arrived on the scene.

Mr Brady said he took his pub's CCTV footage of the incident to the local Garda station and has made a statement.

He has since put the coverage on YouTube where it has been downloaded more than two million times.

The Garda said they are investigating the incident.