GENEVA — As fighting in western Myanmar sent thousands of refugees fleeing to Bangladesh, the United Nations top human rights official on Tuesday urged Myanmar’s military to show restraint and accused the office of the country’s de facto leader, Daw Aung San Suu Kyi, of issuing “irresponsible” statements that could endanger international aid organizations.

United Nations officials said more than 8,700 Rohingya, members of Myanmar’s Muslim minority, have fled across the border to Bangladesh from Rakhine state since Saturday, following clashes last week between security forces and a militant group identified as the Arakan Rohingya Salvation Army. The fighting was reported to have killed more than 100 people.

In comments posted on Facebook on Sunday, Ms. Aung San Suu Kyi’s office said the authorities were investigating reports that staff members of international organizations “had participated” in operations carried out by “extremist terrorists.” It said biscuits supplied by the United Nations food agency had been found at a rebel camp site.