That amounts to 11 percent of the population, it said, citing the Syrian Centre for Policy Research.
A U.S.-led coalition is trying to destroy Daesh militants in Syria and wants the Assad regime to leave. But Russia and Iran are propping up Assad and oppose the opponents of Assad who are being supported by the West its Arab allies such as Saudi Arabia.
About 400,000 of the deaths were directly due to violence, while 70,000 died because they didn't have proper healthcare, medicine, clean water or housing.
It said 1.9 million people had been wounded. Life expectancy has dropped from 70 in 2010 to 55.4 in 2015. Overall economic losses are estimated at $255 billion.
The United States has criticized Russia for killing hundreds of civilians in airstrikes in Syria and accused Moscow of undermining hopes for a cease-fire between the Assad regime and opposition groups.
The Syrian army, supported by Russian air strikes, began a push to retake Aleppo and surrounding areas up to the Turkish border at the start of February.
Russia first began its air campaign in Syria on Sept. 30 of last year.
While Russia claims its campaign is aimed primarily at the Daesh militant group, it has repeatedly targeted civilian areas and the moderate anti-regime opposition groups that control them.
Syria has remained locked in a vicious civil war since early 2011, when the Assad regime cracked down on pro-democracy protests -- which had erupted as part of the "Arab Spring" uprisings -- with unexpected ferocity.
Source: Daily Sabah