Previously, the most paid for a Nobel Prize medal was in 2014, when James Watson - whose co-discovery of the structure of DNA earned him a Nobel Prize in 1962 - sold his medal for $US4.76 million ($A6.86 million).

Three years later, the family of his co-recipient, Francis Crick, received $US2.27 million in bidding run by Heritage Auctions, the same company that sold Muratov's medal on Monday, which was World Refugee Day.

Muratov, who was awarded the gold medal in October 2021, helped found the independent Russian newspaper Novaya Gazeta and was the publication's editor-in-chief when it shut down in March amid the Kremlin's clampdown on journalists and public dissent in the wake of Russia's invasion of Ukraine.

It was Muratov's idea to auction off his prize, having already announced he was donating its accompanying $US500,000 cash award to charity.

The idea of the donation, he said, "is to give the children refugees a chance for a future".

Muratov has said the proceeds will go directly to UNICEF in its efforts to help children displaced by the war in Ukraine.

Melted down, the 175 grams of 23-karat gold contained in Muratov's medal would be worth about $US10,000 ($A14,403).

Muratov told The Associated Press it is important international sanctions levied against Russia do not prevent humanitarian aid, such as medicine for rare diseases and bone marrow transplants, from reaching those in need.

"It has to become a beginning of a flash mob as an example to follow so people auction their valuable possessions to help Ukrainians," Muratov said in a video released by Heritage Auctions, which handled the sale but is not taking any share of the proceeds.

Muratov shared the Nobel Peace Prize last year with journalist Maria Ressa of the Philippines.

The two journalists, who each received their own medal, were honoured for their battles to preserve free speech in their respective countries, despite coming under attack by harassment, their governments and even death threats.

Muratov has been highly critical of Russia's 2014 annexation of Crimea and the war launched in February that has caused nearly five million Ukrainians to flee to other countries for safety, creating the largest humanitarian crisis in Europe since World War II.

Independent journalists in Russia have come under scrutiny by the Kremlin, if not outright targets of the government.

Since Putin came into power more than two decades ago, nearly two dozen journalists have been killed, including at least four who had worked for Muratov's newspaper.

As of early Monday, the high bid for the Nobel medal was $US550,000 ($A792,147). The purchase price had been expected to spiral upward, but perhaps not over $US100 million ($A144 million).

Since its inception in 1901, there have been nearly 1000 recipients of the Nobel Prizes honouring achievements in physics, chemistry, physiology or medicine, literature and the advancement of peace.

Australian Associated Press