Human Rights Watch said Russian aircraft used cluster bombs in two separate raids on the towns of Ruisi and Gori on August 12, killing at least 11 civilians and injuring dozens.
Asked about the report, the deputy chief of Russia's General Staff, Colonel-General Anatoly Nogovitsyn, told a news conference: "We never use cluster bombs. There is no need to do so."
The Gori strike killed at least eight, Human Rights Watch said, including a Dutch cameraman. An Israeli journalist was among the wounded and an armored vehicle belonging to Reuters news agency was perforated with shrapnel.
HRW cited interviews with victims, doctors and military personnel, as well as photos of craters and video footage of the Gori attack, to support its assertion that Russia had used cluster bombs. It said video showed more than two dozen simultaneous explosions during the attack, characteristic of cluster bombs.
More than 100 nations have agreed to ban the use of cluster bombs. Russia has not.
HRW called on Russia to provide precise dates of its cluster attacks "in order to facilitate clean up of the inevitable lingering contamination from cluster bomb submunitions that failed to explode on contact but remain deadly."