An FBI agent has been released without charge after accidentally shooting a man in the leg during a wild dance routine in a US bar.

The agent’s handgun fell from his waistband holster when he attempted a backflip at the establishment in Denver, Colorado, video footage showed.

As the unidentified officer reached to retrieve the gun from the ground, it fired a bullet into the crowd.

“When the agent retrieved his handgun an unintended discharge occurred, another patron was struck by a bullet in the lower leg,” Denver Police Department confirmed in a statement.

The agent then picked up his handgun, tucked it away in his pants and walked away from the incident, footage showed.

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The crowd of onlookers were “shocked after it happened” because he “kind of put his gun back away” and left the scene, Denver police said.

“No one really knew what was going on.”

The injured nightclub onlooker was rushed to hospital and sustained non-life threatening injuries.

Marika Putnam from Devar Police said the agent was taken to Denver police headquarters and released to a FBI supervisor.

Denver police have launched an investigation into the incident which remains a “personnel matter for the FBI,” Denver FBI spokeswoman Amy Sanders said.

The Denver district attorney will decide whether charges should be pressed against the FBI agent.