The Britain-based watchdog expected the death toll to rise.
The hospital was damaged by the attack.
So far, there has been no claim of responsibility.
On Friday, one civilian was killed and 25 others injured in a car bombing in the town of Afrin, also controlled by Turkish-aligned rebels in rural Aleppo, according to the observatory.
Turkey is backing rebel groups fighting to oust Syrian President Bashar al-Assad whose forces, supported by allied Russia, have made military and territorial gains against the opposition in recent months.
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