The governing body of chess said on Friday that it would investigate claims by five-time world champion Magnus Carlsen that American player Hans Niemann had cheated.

The chess world has been shaken for weeks by the Carlsen-Niemann controversy, since Norway's Carlsen withdrew from the Sinquefield Cup in the United States after losing to the 19-year-old.

Last week, Carlsen's abrupt withdrawal from a match against Niemann in the Julius Baer Generation Cup online tournament reignited the furore.

The 31-year-old Carlsen this week for the first time openly accused Niemann of cheating, writing in a letter published on Twitter: "I believe that Niemann has cheated more -- and more recently -- than he has publicly admitted."

Carlsen did not specify the exact form of the alleged cheating, but added there was "more that I would like to say".

Niemann has acknowledged cheating online twice, when he was 12 and 16, but says he has never played fraudulently in a face-to-face match and is even willing to play nude to prove his honesty.

In early September, the huge chess platform chess.com banned the American for cheating on the site.

AFP has previously contacted Niemann for comment.

The International Chess Federation, FIDE, says that it will create an investigatory panel comprising three members of its fair play commission to look into the claims.

"The focus of the investigation would be two-fold: checking the world champion's claims of alleged cheating by Niemann and Niemann's self-statement regarding online cheating," FIDE said.

Salomeja Zaksaite, who chairs the fair play commission, called for an end to the speculation that has dominated the sport in recent weeks.

"In the best interest of the chess community, we would kindly ask the public to refrain from speculations on the outcomes and potential sanctions until all available facts are well considered, and a proper investigation is finalised," said Zaksaite.