An international aid group estimates that at least 6,700 Rohingya Muslims were killed in Myanmar's Rakhine State in violence that broke out there in late August, according to a statement made available Thursday.

Medecins Sans Frontieres, also known by its English name Doctors Without Borders, said its staff met and spoke with Rohingya refugees now sheltered in camps in neighboring Bangladesh and discovered a "staggering" numbers of victims and "horrific" stories of the death of family members in the violence.

It said the figure arrived at through the field survey, covering the period between Aug. 25 and Sept. 24, includes 750 children below the age of 5.

"The findings of MSF's surveys show that the Rohingya have been targeted, and are the clearest indication yet of the widespread violence that started on Aug. 25 when the Myanmar military, police and local militias launched the latest 'clearance operations' in Rakhine in response to attacks by the Arakan Rohingya Salvation Army," it said.

According to the United Nations, more than 600,000 Rohingya Muslims -- a persecuted, stateless minority in predominantly Buddhist Myanmar -- have fled across the border from the northern tip of Rakhine since then.

They have told of atrocities committed by security forces including gang rape, execution-style killings and the razing of entire villages, leading the United Nations to claim that the situation in Rakhine appears to be "a textbook example of ethnic cleansing."

There was no immediate response to the MSF report from Myanmar authorities. They have said the military operation was aimed only at restoring stability and preventing terrorism.