Rohingya children have been beheaded and civilians burned alive, according to witness testimony amid claims that Burma's military and paramilitary forces are committing "genocide" or a "pogrom" against the Muslim minority in the country's western Rakhine state.
Around 60,000 refugees are believed to have fled over the country's western border into Bangladesh in a just a week following a clampdown on Rohingya militants.
The British Foreign Secretary, Boris Johnson, called for the violence to end, saying the treatment of the Rohingya was "besmirching the reputation of Burma", also known as Myanmar, and appealing to Aung San Suu Kyi to act.
Turkey's President, Recep Tayyip Erdogan, has gone much further, accusing Burma's forces of genocide and saying those who turned a blind eye to events were complicit.
Observers believe the number of displaced people is likely to increase. The Burmese military said 400 militants had been killed in clashes with their forces.
Civilians who escaped gave horrific accounts of violence and destruction by Burmese soldiers and other armed groups.
A man named as Abdul Rahman, 41, said he had survived a five-hour attack on Chut Pyin village.
He told Fortifiy Rights, a charity working in the area, that a group of Rohingya men had been rounded up and detained in a bamboo hut, which was then set on fire.
"My brother was killed — [Burmese soldiers] burned him with the group," he said.
"We found [my other family members] in the fields. They had marks on their bodies from bullets and some had cuts.
"My two nephews, their heads were off. One was six years old and the other was nine years old. My sister-in-law was shot with a gun."
Another man from the same village, named as Sultan Ahmed, 27, told the charity: "Some people were beheaded, and many were cut. We were in the house hiding when [armed residents from a neighbouring village] were beheading people.
Survivors from other villages in the region also described seeing people being beheaded or having their throats cut.
"We can't stress enough the urgency of the situation," said Matthew Smith, head of Fortify Rights.
"The Myanmar authorities are failing to protect civilians and save lives. International pressure is critically needed."
Satellite imagery released by Human Rights Watch (HRW) showed 700 buildings burned down in another Rohingya village, Chein Khar Li.
"This new satellite imagery shows the total destruction of a Muslim village, and prompts serious concerns that the level of devastation in northern Rakhine State may be far worse than originally thought," said Phil Robertson, deputy Asia director for HRW.
"Yet this is only one of 17 sites that we've located where burnings have taken place. Independent monitors are needed on the ground to urgently uncover what's going on."
The Burmese government has denied access to the affected areas to journalists and observers.
On Saturday, Mr Johnson, appealed to Aung San Suu Kyi, the former dissident who won the Nobel Peace Prize and is now the country's State Counsellor, to intervene.
"Aung Sang Suu Kyi is rightly regarded as one of the most inspiring figures of our age but the treatment of the Rohingya is alas besmirching the reputation of Burma. She faces huge challenges in modernising her country," he said.
"I hope she can now use all her remarkable qualities to unite her country, to stop the violence and to end the prejudice that afflicts both Muslims and other communities in Rakhine.
"It is vital that she receives the support of the Burmese military, and that her attempts at peacemaking are not frustrated. She and all in Burma will have our full support in this."