Two men have been arrested at the Pokemon World Championships in Boston after they allegedly threatened attendees over social media and were found with a shotgun and assault rifle in their car, local police say.

Security at the Hynes Convention Centre alerted police on Thursday after the threats were reported, and stopped Kevin Norton, 18, and James Stumbo, 27, from entering the competition.

Police later seized their car and found a 12-gauge Remington shotgun, an AR-15 assault rifle, several hundred rounds of ammunition and a hunting knife.

Norton and Stumbo were arrested and charged with unlawful possession of a firearm, unlawful possession of ammunition and other firearm related charges.

Boston Police Department (BPD) superintendent Paul Fitzgerald said they avoided a "potential tragedy".

Loading

"This incident is a good example of private security reaching out to their local Boston police district and relaying information to ... identify the very real threat," he said.

"The BPD detectives and collaborating agencies did a great job in the stop and prevention of a potential tragedy."

The Championships, which began on Friday, sees Pokemon fans battle each other in the trading card game.

The official Pokemon Trading Card Game website listed Norton and Stumbo as invitees in the "masters" division.

The Pokemon Company International said in a statement that "prior to the event this weekend, our community of players made us aware of a security issue".

"Due to quick action, the potential threat was resolved. The Pokemon Company International takes the safety of our fans seriously and will continue to ensure proper security measures are a priority," it said.

Police said the suspects would be arraigned at Boston Municipal Court.