The group, known by its French acronym MSF, said in a statement made available Thursday that it conducted the survey in refugee camps in Bangladesh. It estimated that at least 9,000 Rohingya had died of various causes in Myanmar's Rakhine state between Aug. 25 and Sept. 24, and that more than 70 percent of the deaths were the result of violence.

According to MSF, the dead included at least 730 children younger than 5.

More than 630,000 Rohingya Muslims have fled Buddhist-majority Myanmar into Bangladesh to escape what the United Nations has called "ethnic cleansing."

"The peak in deaths coincides with the launch of the latest 'clearance operations' by Myanmar security forces in the last week of August," MSF medical director Sidney Wong said in a statement.

She said the findings were staggering, both in terms of the numbers of people who reported a family member died as a result of violence and the horrific ways in which they said they were killed or severely injured.

MSF said that among children below the age of 5, more than 59 percent who were killed during that period were reportedly shot, 15 percent burnt to death in their homes, 7 percent beaten to death and 2 percent died due to landmine blasts.

Myanmar's Information Ministry has said that 400 people died following attacks by a militant Rohingya group on police posts on Aug. 25. It said most of the 400 were "extremist terrorists" who died during military "clearance operations."

International aid and rights groups have accused the military of arson, killings and rapes of Rohingya villagers. Myanmar authorities have blamed Rohingya militants for the violence.

More than 1 million ethnic Rohingya Muslims have lived in Myanmar for generations. They have been stripped of their citizenship, denied almost all rights and labeled stateless.

Since the Myanmar's military conducted operations against the Rohingya in Rakhine state, the civilian government has barred most journalists, international observers and humanitarian aid workers from independently traveling to the region.

MSF said the number of deaths is likely to be an underestimation "as we have not surveyed all refugee resettlements in Bangladesh and because the surveys don't account for the families who never made it out of Myanmar."

AP