The pair were competing at the Julius Baer Generation Cup when Carlsen turned off the screen and left the match without explanation – the latest twist in an apparent feud between the two players.
CNN has reached out to a representative for Carlsen for comment but did not receive a response.
Earlier this month, the Norwegian withdrew from the Sinquefield Cup in Saint Louis after a surprise defeat to American star Niemann – the first time he withdrew from a tournament in his career, according to chess24.
The 19-year-old admitted to cheating at the ages of 12 and 16 but said in an interview with St. Louis that he has never cheated in board games.
“I’m telling my truth because I don’t want any distortion,” Niemann said. “I’m proud of myself that I learned from that mistake, and now I gave everything to chess. I sacrificed everything for chess.”
The tension between Niemann and Carlsen rocked the chess community. Niemann said he was removed from the popular website Chess.com after Carlsen’s tweet and that “the whole social network and the chess world are completely attacking me and weakening me.”
“Seeing my absolute hero (Carlsen) try to take aim, try to ruin my reputation, ruin my chess career and do it so frivolously really, really disappointing,” he added.
Neither Niemann nor Chess.com responded to CNN’s request for comment.
Rensch continued: “We invited Hans to provide explanation and feedback in hopes of finding a solution so that Hans can rejoin on Chess.com.”
Carlsen and Niemann played two more games against other opponents after the former player unexpectedly resigned on Monday. Carlsen is two points behind leader Arjun Erigaisi in the league standings after eight rounds, while Niemann is four points behind.
“It looks very odd now. Obviously, it all makes sense if, supposedly, Hans is cheating and he doesn’t want to play him, but if he’s not (cheating), then it’s real. very wrong.
“So I don’t know, we’ll have to see. Again, people are expecting some kind of big rabbit from the hat with Magnus, but it doesn’t seem like he wants to play Hans.”
Levon Aronian, who is also competing in the tournament, said Niemann “isn’t the cleanest person when it comes to online chess,” but added that “this is a problem that needs a solution.”
CNN’s Ben Morse contributed to the reporting.