Pro-Assad forces, backed by Russian jets, launched an attack on rebel-held towns north of the city of Homs on Thursday, Reuters and local activists said.
The Russian air strikes hit targets around the town of Talbiseh and the villages of Teir Malla, Dar Kabira and Khalidiya, a few miles north of the mainly government-held city, the Syrian Observatory for Human Rights said.
Zaman al-Wasl correspondent said 13 people, mostly children, were killed when Russian jets struck a bakery in Teir Malla village. Syrian soldiers and fighters from Lebanon's Hezbollah were involved in the assault.
Hezbollah's al-Manar television channel said the Syrian army was carrying out a ground offensive in northern Homs province.