The top UN human rights official has denounced Myanmar's "brutal security operation" against Muslim Rohingyas in Rakhine state, saying it is disproportionate to insurgent attacks carried out last month.
Communal tensions appeared to be rising across Myanmar on Monday after two weeks of violence in Rakhine state that have triggered an exodus of about 300,000 Rohingya Muslims, prompting the government to tighten security at Buddhist pagodas.
Zeid Ra'ad al-Hussein, addressing the United Nations Human Rights Council on Monday, said more than 270,000 people had fled to Bangladesh, with more trapped on the border, amid reports of the burning of villages and extrajudicial killings.
"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," Zeid said.
He cited reports that Myanmar authorities had begun to lay landmines along the border with Bangladesh and would require returnees to provide "proof of citizenship".
"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," Zeid said.
"The situation seems a textbook example of ethnic cleansing."
His comments came after a mob of about 70 people armed with sticks and swords threatened to attack a mosque in the central town of Taung Dwin Gyi on Sunday night, shouting "This is our country, this is our land", according to the mosque's imam, Mufti Sunlaiman.
Authorities say the mob was dispersed after police with riot shields fired rubber bullets.
Rumours have spread on social media that Muslims, who represent about 4.3 per cent of the Buddhist-majority country's population of 51.4 million, would stage attacks on September 11 to avenge violence against the Rohingya in northern Rakhine.
Attacks by Arakan Rohingya Salvation Army (ARSA) militants on police posts and an army base on August 25 provoked a counter-offensive and a mass migration of villagers into the Cox's Bazar region of southern Bangladesh.
Myanmar says its security forces are carrying out clearance operations to defend against ARSA, which the government has declared a terrorist organisation.