A man who fired an assault rifle in a pizza restaurant in Washington DC claims he was investigating a conspiracy theory about Hillary Clinton.

Edgar Maddison Welch, 28, pointed a firearm at an employee as he walked through the door of Comet Ping Pong.

The restaurant became notorious during the presidential election campaign after a number of fake news stories claimed Hillary Clinton and her campaign chief ran a child sex ring out of the eatery.

The employee was able to flee and call police, at which point Welch is said to have fired the gun into the floor.

No one was injured in the shooting.

Police have since arrested Welch and he has been charged with assault with a dangerous weapon.

Welch told police he had come to the restaurant to "self-investigate" the online conspiracy theory.

The owner of Comet Ping Pong, James Alefantis, released a statement calling the stories "malicious and utterly false accusations".