The UN human rights chief says he strongly suspected that "acts of genocide" may have taken place against Muslim Rohingyas in Myanmar's northern Rakhine state since August.
Zeid Ra'ad al-Hussein, in a speech to the United Nations Human Rights Council, also said reports of bulldozing of mass graves in Myanmar showed a "deliberate attempt by the authorities to destroy evidence of potential international crimes, including possible crimes against humanity".
"A recent announcement that seven soldiers and three police officers will be brought to justice for the alleged extra-judicial killing of ten Rohingya men is grossly insufficient," Mr al-Hussein told the Geneva forum on Wednesday (local time).
Nearly 700,000 Rohingya have fled military operations to Bangladesh, bringing with them tales of killings, rape, and arson by Myanmar security forces.
The UN assistant secretary general for human rights, Andrew Gilmour, said on Tuesday that ethnic cleansing was continuing in Myanmar.
"It appears that widespread and systematic violence against the Rohingya persists," Mr Gilmour said after visiting refugee camps in Bangladesh.