Speaking in a news conference in Geneva on Friday, Zeid Ra’ad al-Hussein also urged Myanmar to allow monitors into restricted areas to investigate what he called suspected "acts of genocide".
If they want to disprove the allegations of serious violations against the Rohingya, "invite us in" to Rakhine State, Zeid added.
"We are saying there are strong suspicions that, yes, acts of genocide may have taken place. But only a court can confirm this," the UN High Commissioner for Human Rights emphasized.
Zeid had previously described Myanmar's campaign against the Rohingya as a "textbook case of ethnic cleansing".
Myanmar has consistently denied that any violence has taken place against the Rohingya Muslims despite the widespread and well-documented accounts of horrific violence.
The Rohingya, viewed by the UN and the US as one of the most persecuted communities in the world, have faced widespread discrimination from Myanmar authorities.
Since August, more than 650,000 Rohingya have fled to Bangladesh after the Myanmar's military cracked down on the minority in northern Rakhine State.
