Police in Washington, D.C. have arrested a man who entered a pizza restaurant in the city armed, claiming he wanted to "self-investigate" an conspiracy theory involving Hillary Clinton known colloquially as "pizzagate".

Edgar Maddison Welch, 28, of Salisbury, North Carolina, entered Comet Ping Pong just before 3pm on Sunday 4 December, police said. According to a police statement, Welch pointed a gun at an employee who managed to flee and alert the authorities.

Welch "proceeded to discharge the rifle inside the establishment," police said, adding that no one was reported injured and police were able to arrest Welch "without incident".

Two weapons were found in the restaurant and an additional weapon was found in Welch's car. He has been charged with assault with a dangerous weapon.

Police said that during an interview after his arrest, Welch told them that he had attended the restaurant to "self-investigate" the so-called "pizzagate" online conspiracy theory.

Pizzagate is a conspiracy theory spread between fake news sites and anti-Clinton social media accounts. It accuses Bill and Hillary Clinton of using the Comet Ping Pong pizza restaurant as a front for a paedophile ring. There is no evidence behind the accusations and, as a Buzzfeed News analysis showed earlier this year, the story came mostly from websites looping false claims originating from a white-supremacist website.

Social media users posted pictures and videos showing a heavy police presence around the restaurant on Sunday.

The owner of the restaurant, James Alefantis, thanked police in a statement and condemned people who "spread malicious and utterly false accusations about Comet Ping Pong."

"What happened today demonstrates that promoting false and reckless conspiracy theories comes with consequences," said Alefantis, according to the New York Daily News. "I hope that those involved in fanning those flames will take a moment to contemplate what happened here today, and stop promoting these falsehoods right away."