BILLINGS, Mont. — Chess’s international governing body on Friday suspended former world champion Vladimir Kramnik for at least a year after he leveled unproven allegations of cheating against other players, including Daniel Naroditsky, who died last year at age 29.

Kramnik accused Naroditsky of cheating last year and continued to share suspicions on social media. Naroditsky, a prodigious American chess player and grandmaster who helped fuel the rise of online gaming with educational videos and live streams on YouTube, denied the allegations.

Kramnik said in an email to The Associated Press that he plans to appeal the suspension.

“I am absolutely sure that this illegal verdict will ultimately be overturned and I intend to pursue all necessary steps to the end to restore justice and, in particular, my reputation,” Kramnik said in a social media post.

The chess federation said Kramnik publicly alleged cheating without “adequate evidentiary support,” violating its rules against cyberbullying.

The federation said combating cheating was one of its priorities, but that allegations must be addressed through its procedures and supported with appropriate evidence.

“It exposed identifiable players to unjustified harm to their reputation and undermined the safeguards established by the disciplinary framework,” federation representatives said in their decision.

Naroditsky was found dead in his North Carolina home in October. He died from an abnormal heartbeat caused by an accidental overdose, according to a toxicology report.

Naroditsky had said before his death that Kramnik’s accusations had taken their toll on him.

“Since Kramnik, I feel like if I start doing it right, people assume the worst intentions. The problem is just the lingering effect of it,” Naroditsky said in his last live broadcast before his death.

Kramnik called Naroditsky’s death a tragedy. He said there had been a cynical campaign to link him to Naroditsky’s death without any factual basis.