A new report has found that at least 9,000 Rohingya have died in Myanmar, in Rakhine state, between August 25th and September 24th.
Surveys were conducted by the medical charity Médecins Sans Frontières/Doctors Without Borders (MSF) in refugee settlement camps in Bangladesh.
They estimate that at least 9,000 Rohingya died in Myanmar in the same month.
But it says as 71.7% of the reported deaths were caused by violence, at least 6,700 Rohingya are estimated to have been killed "in the most conservative estimations".
This includes at least 730 children below the age of five years.
The findings show that the Rohingya have been targeted, and - it says - are the clearest indication yet of widespread violence that started on August 25th when the Myanmar military, police and local militias launched "clearance operations" in Rakhine.
Since then, more than 647,000 Rohingya have fled from Myanmar into Bangladesh.
Dr Sidney Wong, MSF medical director, says: "We met and spoke with survivors of violence in Myanmar, who are now sheltering in overcrowded and unsanitary camps in Bangladesh.
"What we uncovered was 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.
"The peak in deaths coincides with the launch of the latest 'clearance operations' by Myanmar security forces in the last week of August".
In early November MSF conducted six retrospective mortality surveys in different sections of the refugee settlements in Cox's Bazar, just over the border from Myanmar.
The total population of the areas covered by the surveys was 608,108 people - 503,698 had fled Myanmar after August 25th. 100,464 were children below the age of five years.
The overall mortality rate between August 25th and September 24th of people in households surveyed was 8.0/10,000 persons per day.
MSF says this is equivalent to the death of 2.26% of the sampled population.
If this proportion is applied to the total population that had arrived since August 25th in the camps which were covered by the surveys, it would suggest that between 9,425 and 13,759 Rohingya died during the initial 31 days following the start of the violence, including at least 1,000 children below the age of five years.
Some readers may find elements of these details distressing
The surveys show that of these deaths at least 71.7% were due to violence, including among children under five years old.
Overall, gunshots were the cause of death in 69% of the violence-related deaths, followed by being burnt to death in their houses (9%) and beaten to death (5%).
Among children below the age of five years, more than 59% killed during that period were reportedly shot, 15% burnt to death in their home, 7% beaten to death and 2% died due to landmine blasts.
"The numbers of deaths are likely to be an underestimation as we have not surveyed all refugee settlements in Bangladesh and because the surveys don’t account for the families who never made it out of Myanmar," Dr Wong says.
"We heard reports of entire families who perished after they were locked inside their homes, while they were set alight."
"Currently people are still fleeing from Myanmar to Bangladesh and those who do manage to cross the border still report being subject to violence in recent weeks.
"With very few independent aid groups able to access Maungdaw district in Rakhine, we fear for the fate of Rohingya people who are still there."
Read the report in full here