At least 14 civilians, nearly half of them children, were killed on Friday in air strikes on a flashpoint town in central Syria, a monitoring group said.
Six children and five women were among those killed in the aerial attack on Talbisseh in Homs province, according to Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
He said the air raids were believed to have been carried out by either Russia or the Syrian regime, both of which have been conducting air strikes in the area.
Moscow has been carrying out raids throughout Syria on what it says are Islamic State jihadist group targets since September 30.
Russia's air force has been backing ground operations by the Syrian army in the coastal province of Latakia as well as Aleppo in the north, and Homs and Hama in the war-ravaged country's centre.
A US-led coalition has also conducted more than a year of air strikes in Syria as part of its war on IS.
Talbisseh, which lies on the highway between Homs and Hama, is controlled by non-IS rebel forces and Syria's Al-Qaeda affiliate Al-Nusra Front.
Late Thursday, more than a dozen Russian raids on the IS stronghold of Raqa city killed at least 18 people, 11 of them jihadists, said the Britain-based Observatory.
"Seven civilians, including two children, were killed in strikes by Russian planes," and 11 IS members were killed in raids on several IS bases in the city, the monitor said.
It said more than 30 people were wounded in the attack.
Russian warplanes on Friday struck targets in eastern parts of Hama province, southern battlefronts in Aleppo province, and parts of the regime bastion of Latakia province, the Observatory said.
The monitor relies on a network of activists, medical staff and fighters on the ground who identify Russian warplanes based on model, flight patterns and munition types.
Moscow has dismissed its previous reports of civilian casualties from its bombing as "fake".
