Observatory head Rami Abdel Rahman said warplanes bombarded Raqa, the Islamic State group's de facto Syrian capital, as well as the towns of Azaz and Al-Bab in Aleppo province, on Thursday.
Six children and 11 women were among the dead, and dozens of people were wounded, the Britain-based monitor said.
The toll in Raqa also included two rescue workers, according to Abdel Rahman, but he said no suspected militants were killed in the three areas that were hit.
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Russia has been conducting an intense air war on armed opposition groups throughout Syria for nearly three months.
But its campaign has been criticised by the West and by rebels for targeting non-jihadist groups and incurring civilian casualties.
The Observatory says it distinguishes between strikes carried out by Syrian, Russian and US-led coalition aircraft based on flight patterns indicating whether planes took off from inside the country, as well as the type of planes and ordnance used.
It identifies those killed through its broad network of activists, medical workers at local hospitals, and fighters on the ground.
More than 250,000 people have been killed since Syria's conflict erupted in 2011.