UNICEF's Patrick McCormick said the death toll included children, as reports of another 103 dead surfaced on Sunday, CNN reported.
August was also the country's bloodiest month so far, as almost 5,000 people died in August, according to the Center of Documentation of Violation in Syria.
Last week alone, Syrian rebels and activists reported a massacre of between 300 and 600 people in the Damascus suburb of Daraya by government forces, the Associated Press reported.
As the AP pointed out:
The civil war witnessed a major turning point in August when Assad's forces began widely using air power for the first time to crush the revolt. The fighting also reached Syria's largest city, Aleppo, which had been relatively quiet for most of the 17-month-old revolt.
However, McCormick did not explain how he arrived at the figure, and the death tolls in the region are difficult to verify, CNN reported.