(CNN) At least 6,700 Rohingya were killed in attacks during the first month of a military crackdown in Myanmar in late August, Médecins Sans Frontières estimates.

The aid group interviewed several thousand Rohingya refugees in four camps in Bangladesh in late October and early November, asking how many members of their families had died and how, both before and after the violence began.

The survey showed that a minimum of 6,700 Rohingya -- including 730 children -- were killed by shooting and other violence between August 25 and September 24, and that at least 2,700 others died from disease and malnutrition, according to MSF.

The aid agency's death toll far surpasses estimates from Myanmar's government, which has put the figure in the hundreds.

More than half a million Rohingya have fled northwestern Myanmar into Bangladesh since a concerted military crackdown began in late August, following militant attacks on a border post. Both the UN and the US have described the campaign as ethnic cleansing.

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