The airstrike carried out on Sunday by the Russian air force on a busy market place in Idlib province, Syria, killed more than 40 people and wounded dozens more, reports said.
Russian jets bombed the town of Ariha, in north-west Syria as part of its massive air campaign that targets the Islamic State (ISIS) and other militants in Syria. But the place is apparently a town controlled by opposition forces and not an ISIS stronghold, said the Daily Mail.
In addition to the market, several other areas of the town were hit, activists told Aljazeera.
Local news channel Ariha al-Youm reported that cluster bombs were used in the raid by a Russian jet, the report said.
"The vendors were shouting loudly as people were buying and selling and suddenly we heard the sound of the planes and in less than a second the jets struck and there was deadly silence,'' said Mohamed Queissi, a rescue worker with the civil defence service that operates in rebel-held areas, ABC.Net reported.
"I saw people thrown in the street, strewn corpses and terrified children cying and shouting for their parents,'' added Mohamed Amine Qurabi, a second civil defence worker.
Given the scope of the damage, the Syrian Observatory for Human Rights believes that the death toll from the attack could be much higher or as many as 60.
Photos and videos of the wreckage it posted online in the aftermath of the bombing showed survivors desperately trying to pull the wounded from burning rubble, while dead bodies litter the streets and hospital corridors covered in blood.
Ariha in Idlib province is an area controlled by anti-government forces, including the al Qaeda-linked Nusra Front.
Russia, which began airstrikes late September, claims it is targeting ISIS and other "terrorists." But members of the U.S.-led coalition say most of the strikes have focused on central and northern Syria, where ISIS does not have a strong presence.
Russia supports President Bashar al-Assad, who has been fighting against rebel groups since March 2011.
Ariha fell to Syrian rebel forces in May during an advance that resulted in the whole of Idlib province falling to the rebellion against President Bashar al-Assad, the report said.