At least 12 jihadists from Daesh group have been killed in Russia's first air strikes on the extremist faction's main Syrian bastion, a monitoring group said.

"Last night, Russian strikes on the western edges of Raqa city, and near the Tabqa military airport, killed 12 Daesh jihadists," Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, said on Friday.

He said their bodies were transported to a hospital in the province.