US players of the League of Legends video game have had personal details including credit card details, email addresses and usernames hacked. Developers Riot Games confirmed in a statement on their blog that their records had been accessed.

“We’re really sorry to share that a portion of North American account information was compromised,” it said. “Usernames, email addresses, salted password hashes, and some first and last names were accessed.”

Although the passwords had been protected, the company advised that any gamers with “easily guessable passwords” were vulnerable to account theft. Riot Games is also looking into 120,000 transaction records from 2011 that may have been hacked to find out if users’ credit card details have been leaked. “Our investigation is ongoing and we will take all necessary steps to protect players,” the company said.

The company is requesting that US users update their passwords and said they were in the process of introducing new security measures. “We’re sincerely sorry about this situation,” the firm added. “We apologize for the inconvenience and will continue to focus on account security going forward.” We’re really sorry to share that a portion of our North American account information was recently compromise

Last month the US issued League of Legends players with athlete visas, effectively recognising the video game as a professional sport. Players were given P-1 visas, intended for “individual athletes”. The move was described as “groundbreaking” for eSports, a growing community of professional gamers. More than 40 million people worldwide play League of Legends.

The biggest tournaments are attended by tens of thousands of fans and receive coverage on dedicated TV channels. Winners of the League of Legends Season 3 World Championship starting in September will win $1 million (£662,000) in prize money.