The top U.N. rights official said Monday that Myanmar authorities' "brutal security operation" in strife-torn Rakhine State appears to be "a textbook example of ethnic cleansing" against the country's persecuted, stateless Rohingya people.

Zeid Ra'ad Al Hussein, the U.N. high commissioner for human rights, said in an address to the Human Rights Council that the military operation, prompted by Rohingya militants attacks on police posts on Aug. 25, "is clearly disproportionate and without regard for basic principles of international law."

"We have received multiple reports and satellite imagery of security forces and local militia burning Rohingya villages, and consistent accounts of extrajudicial killings, including shooting fleeing civilians," he said.

"Because Myanmar has refused access to human rights investigators, the current situation cannot yet be fully assessed, but the situation seems a textbook example of ethnic cleansing."

The crackdown has caused more than 290,000 people flee across the border to Bangladesh over the last three weeks.

Zeid said he was "appalled" by reports that the Myanmar authorities have now begun to lay landmines along the border with Bangladesh, and that refugees who have fled the violence will only be allowed back if they can provide "proof of nationality."

"Given that successive Myanmar governments have since 1962 progressively stripped the Rohingya population of their political and civil rights, including citizenship rights...this measure resembles a cynical ploy to forcibly transfer large numbers of people without possibility of return," he said.

Rohingya Muslims represent the largest percentage of Muslims in predominantly Buddhist Myanmar, with the majority living in Rakhine. They self-identify as a distinct ethnic group with their own language and culture, and many have lived in Myanmar for generations.

But the government does not recognize them as one of the country's many ethnic groups, considering them instead to be illegal migrants from Bangladesh, and they are often portrayed by ultra-nationalist Buddhist groups as a "threat to race and religion."

Against this backdrop, communal tensions have occasionally erupted into violence.

Many Rohingya live in extreme poverty and in fear of arbitrary arrest and detention, while they are denied freedom of movement and have limited access to education and healthcare.

Last year, Zeid warned that the pattern of gross violations of their human rights possibly amounts to crimes against humanity.

In his address Monday, he also urged the Myanmar government to "stop claiming that the Rohingyas are setting fire to their own homes and laying waste to their own villages."

"This complete denial of reality is doing great damage to the international standing of a government which, until recently, benefited from immense good will," he said.