According to the Syrian Observatory for Human Rights, seven children and six women were among those killed in at least 40 air raids on areas in the countryside of Idlib, Xinhua news agency reported.
The UK-based watchdog said the airstrikes targeted the towns of Sarmin, Jisr al-Shughour, etc. and other areas in Idlib's countryside.
The death toll is likely to rise due to a large number of critically wounded people, the organisation added.
Much of Idlib has fallen to the rebels over the past year, except two Shiite towns loyal to the government.
The rebels who are fleeing or evacuating areas under their control in the capital Damascus or in the city of Aleppo were all headed toward Idlib, making the province increasingly heavy with armed militants.