GENEVA — Myanmar’s civilian leader, a Nobel laureate once extolled as a champion of democracy, could face prosecution for crimes against humanity because of the military’s attacks on Rohingya Muslims and other minority groups, United Nations investigators said on Tuesday.

Their statement was a new sign of how far the leader, Daw Aung San Suu Kyi, had fallen from grace in the three years since she took office, overshadowed by the military’s campaign against the Rohingya.

She was first acclaimed as an icon of the pro-democracy movement in Myanmar, having won the Nobel Peace Prize in 1991 and endured many years of house arrest. Now she has become an international pariah for her government’s response to brutal oppressions by Myanmar’s military.

In a report to the United Nations top human rights body in Geneva on Tuesday, a panel of investigators, the Independent International Fact-Finding Mission on Myanmar, said the 660,000 Rohingya people who remain in Myanmar face systematic persecution.