Originally Published: 20 SEP 22 09:41 ET

Updated: 20 SEP 22 11:13 ET

By George Ramsay, CNN

(CNN) -- Shortly after making his first move, world champion Magnus Carlsen resigned from an online chess match against fellow grandmaster Hans Niemann on Monday.

The pair were playing in the Julius Baer Generation Cup when Carlsen turned off his screen and left the match without explanation -- the latest twist in an apparent feud between the two players.

"We're going to try and get an update on this," commentator Tania Sachdev said in a live broadcast of the match on chess24. "Magnus Carlsen just resigned -- got up and left, switched off his camera and that's all we know right now."

CNN has contacted Carlsen's representatives for comment but did not receive a response.

Earlier this month, the Norwegian withdrew from the Sinquefield Cup in Saint Louis following his surprise defeat against American star Niemann -- the first time he has withdrawn from a tournament in his career, according to chess24.

Carlsen confirmed his withdrawal on Twitter, posting: "I've withdrawn from the tournament. I've always enjoyed playing in the @STLChessClub, and hope to be back in the future." Carlsen's tweet also included a well-known video of football manager Jose Mourinho saying: "If I speak, I am in big trouble."

Another grandmaster, Hikaru Nakamura, said Carlsen is "suspicious" of Niemann's conduct, and days after the Sinquefield Cup match, Niemann publicly responded to allegations that he had cheated earlier in his chess career.

The 19-year-old admitted to cheating at the ages of 12 and 16 but said in an interview with the St. Louis Chess Club he had never cheated in over-the-board games.

"I'm saying my truth because I do not want any misrepresentation," said Niemann. "I am proud of myself that I have learned from that mistake, and now I have given everything to chess. I have sacrificed everything for chess."

The tension between Niemann and Carlsen has rocked the chess community. Niemann said he had been removed from popular website Chess.com following Carlsen's tweet and that "the entire social media and chess world is completely attacking me and undermining me."

"To see my absolute hero (Carlsen) try to target, try to ruin my reputation, ruin my chess career and to do it in such a frivolous way is really, really disappointing," he added.

Neither Niemann nor Chess.com responded to CNN's request for comment.

In a statement on September 8, Chess.com's Chief Chess Officer Danny Rensch said the site had "shared detailed evidence with [Niemann] concerning our decision, including information that contradicts his statements regarding the amount and seriousness of his cheating."

Rensch continued: "We have invited Hans to provide an explanation and response with the hope of finding a resolution where Hans can again participate on Chess.com."

Carlsen and Niemann played two further games against other opponents following the former's sudden resignation on Monday. Carlsen is two points behind leader Arjun Erigaisi in the tournament standings after eight rounds, while Niemann is four points back.

"It looks like he (Carlsen) is clearly insinuating something, but until you catch someone, you cannot do anything," Anish Giri, who is also competing at the Julius Baer Generation Cup, told chess24.

"It just looks very odd now. Clearly, it all makes sense if, supposedly, Hans is cheating and he doesn't want to play him, but if he isn't (cheating), then it is really very wrong.

"So I don't know, we have to see. Again, everybody is expecting some kind of big rabbit from the hat with Magnus, but he just doesn't want to play Hans, it seems."

Levon Aronian, who is also competing in the tournament, said Niemann "has been not the cleanest person when it comes to online chess," but added that "this is a problem that requires a solution."