Rights group Amnesty International has released satellite images which it says show an “orchestrated campaign” to burn Rohingya villages in western Myanmar.
Amnesty said this was evidence security forces were trying to push the minority Muslim group out of the country.
The army says it is fighting militants and denies targeting civilians.
Some 389,000 Rohingya have fled to Bangladesh since violence began last month. They have long been persecuted in Myanmar as “illegal immigrants”.
At least 30% of Rohingya villages in Rakhine state are now empty, the government says.
They have lived in the state in Myanmar, also known as Burma, for generations but are denied citizenship.
Myanmar has faced international condemnation over the crisis.
On Thursday US Secretary of State Rex Tillerson said Myanmar’s democracy was facing a “defining moment”.
“I think it is important that the global community speak out in support of what we all know the expectation is for the treatment of people regardless of their ethnicity,” he said in London.
“This violence must stop, this persecution must stop.”
A day earlier UN Secretary General Antonio Guterres said the Rohingya were facing a catastrophic humanitarian situation, and attacks on villagers were unacceptable. The UN Security Council has called for urgent steps to end the violence.
Amnesty said it had new evidence based on fire-detection data, satellite imagery, photos and videos, as well as interviews with eye-witnesses, of “an orchestrated campaign of systematic burnings” targeting Rohingya villages for almost three weeks.
“The evidence is irrefutable – the Myanmar security forces are setting northern Rakhine State ablaze in a targeted campaign to push the Rohingya people out of Myanmar. Make no mistake: this is ethnic cleansing,” said Tirana Hassan, the group’s crisis response director.
Amnesty said security forces would surround a village, shoot people as they fled and burn down their houses, describing the acts as “crimes against humanity”.
It said it had detected at least 80 major fires in inhabited areas since 25 August, following attacks on police posts by the rebel Arkan Rohingya Salvation Army (Arsa).
No fires of this magnitude had been seen in similar periods over the last four years, Amnesty added.
The rights group said it had also received credible reports of Rohingya militants burning homes of Buddhist ethnic Rakhine but had been unable to verify them.
Myanmar’s envoy to the UN has blamed the Rohingya insurgents for the violence in Rakhine state and said that his country would never tolerate such atrocities. (Courtesy BBC)