Zeid Ra'ad al-Hussein, addressing the UN human rights council in Geneva, said the UN had 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".

"I call on the government to end its current cruel military operation, with accountability for all violations that have occurred, and to reverse the pattern of severe and widespread discrimination against the Rohingya population," he said.

Almost 300,000 distressed Rohingya have fled violence in Rakhine province in the past fortnight, creating what aid agencies say is one of the worst humanitarian crises in Asia for decades.

The Brussels-based International Crisis Group warns that an "alienated, desperate and dispossessed" Rohingya population is now ripe for exploitation by jihadists.

"The events of recent weeks are not just causing enormous suffering to civilians, but bring Myanmar precipitously close to unravelling much that has been achieved since the end of military rule," the group said in its latest statement on the crisis.

"The risks to those who live in Myanmar, the country's transition and regional stability are considerable."

Michael Vatikiotis, Asia director of the conflict resolution group Centre for Humanitarian Dialogue, says Rakhine has become a "nightmare" for the 10-member Association of South-East Asian Nations, which is already plagued by multiple violent armed conflicts, including the three-month siege of the southern Philippine city of Marawi by Islamic State-aligned fighters.

"The problem is that in both Indonesia and Malaysia, where anger towards Myanmar is building, there is a risk that the plight of the Rohingya could become a lightning rod for underlying divisions between Muslims and non-Muslims, which in turn is being exploited by politicians with domestic agendas," he said.

Mr Vatikiotis said counter-insurgency strategies by Myanmar security forces after attacks on police posts in late August by Rohingya insurgents were unlikely to have much affect on the crisis involving more than one million stateless people.

He said many nearby countries worry what would happen if more Rohingya were forced from Rakhine.

"Where do they go? And how does South-East Asia suddenly confront a desperate diaspora problem akin to the Palestinian issue that has perpetuated violent conflict in the Middle East for 70 years," said Mr Vatikiotis, author of Blood and Silk, a just-released book that chronicles the region's conflicts.

Tensions are also rising in South Asia over the crisis.

Protest rallies have been held across Pakistan to condemn what organisers describe as the "persecution" of Rohingya.

Bangladesh's Foreign Minister Abul Hassan Mahmud Ali describes the violence in Rakhine as "genocide" and says thousands have been killed.

Communal tensions are also rising across Myanmar.

Mobs attacked a mosque in the central town of Taung Dwin Gyi shouting "this is our country, this is our land".

Prince Zeid's comments will intensify international pressure on Myanmar's leader Aung San Suu Kyi to intervene to stop the bloodshed.

But the Noble laureate has been steadfast in her defence of her country's military, which claims it is responding to attacks by Rohingya insurgents and denies targeting civilians.

There is widespread hatred of Rohingya among Myanmar's majority Buddhists who regard them as illegal "Bengali" immigrants.

Prince Zeid said he is "appalled" by reports that Myanmar authorities have begun to lay internationally banned landmines along the border with Bangladesh to stop fleeing Rohingya.

He said statements by Myanmar officials that Rohingya who cross into Bangladesh would not be allowed to return unless they provided proof of nationality "resembles a cynical ploy to forcibly transfer large numbers of people without possibility of return".

Myanmar denies Rohingya citizenship and other basic rights despite that fact that they have lived in Rakhine for generations.

"The Myanmar Government should stop claiming that the Rohingya are setting fire to their own homes and laying waste to their own villages," the prince said.

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