However, the official reportedly cautioned that calculating loss of life during a war is difficult and may not always be completely accurate.
The war has been extremely costly for Ukraine as well. The official said up to 4,000 Ukrainian troops have been killed in the conflict, CBS News reported. The Ukrainian government reports that hundreds of civilians have also died from Russian attacks.
The conflict has been going on for more than two weeks, and there is no sign of it easing.
On Thursday, Ukraine's foreign minister says talks between the top diplomats of Moscow and Kyiv produced no breakthrough on ending the war.
Ukrainian Foreign Minister Dmytro Kuleba said he attended the meeting Thursday with Russian Foreign Minister Sergey Lavrov in Turkey to discuss humanitarian corridors and a cease-fire.
Lavrov said Russia was ready for more negotiations but showed no sign of softening Moscow's stance in the dispute.