The Nobel Peace Prize to Aung San Suu Kyi will not be withdrawn in the light of a United Nations report that said Myanmar's military carried out mass killings of Muslim Rohingya, the Norwegian Nobel Committee said on Wednesday.

On Monday, UN investigators said Myanmar's military carried out mass killings and gang rapes with "genocidal intent", and the commander-in-chief and five generals should be prosecuted for the gravest crimes under international law.

Aung San Suu Kyi, who leads the Myanmar government and won the Nobel Peace Prize in 1991 for campaigning for democracy, has been criticised for failing to speak out against the army crackdown in Rakhine State.

"It's important to remember that a Nobel Prize, whether in Physics, Literature or Peace, is awarded for some prize-worthy effort or achievement of the past," said Olav Njoelstad, the secretary of the Norwegian Nobel Committee.

"Aung San Suu Kyi won the Nobel Peace Prize for her fight for democracy and freedom up until 1991, the year she was awarded the prize," he said.

And the rules regulating the Nobel Prizes do not allow for a prize to be withdrawn, he added.

The Norwegian Nobel Committee consists of a panel of five Norwegians, mostly former politicians and academics, that reflect the different forces in the Norwegian Parliament. The other Nobel prizes are awarded in Sweden.

Last year, the head of the Committee, Berit Reiss-Andersen, also said it would not strip the award after previous criticism of Aung San Suu Kyi's role in the Rohingya crisis.

"We don't do it. It's not our task to oversee or censor what a laureate does after the prize has been won," she said in a television interview. "The prize winners themselves have to safeguard their own reputations."