"We have documented the deaths of 31 civilians, among them five women and three children, in Raqa and its surroundings," said Syrian Observatory for Human Rights director Rami Abdel Rahman yesterday.
Another 15 jihadists were confirmed dead in a string of eight air strikes, as well as seven other unidentified people.
Eight of the civilian victims were from one family, said Abdel Rahman.
The strikes come amid a stepped-up campaign by President Bashar al-Assad's regime targeting IS positions in northern and eastern Syria.
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Similar strikes on Tuesday in the eastern province of Deir Ezzor killed 16 people, including 10 children.
The targets yesterday included a building housing an IS Islamic court and a training camp. Twenty-four of the dead were killed when a bakery was hit.
The Islamic State group first emerged in Syria's war in late spring 2013, when it was named the Islamic State of Iraq and the Levant (ISIL).
Its horrific abuses, including near-daily public executions, have made it widely feared in areas it controls, but activists say people mostly stay silent for fear of reprisals.
Insurgent areas of Aleppo have come under massive aerial bombardment since December, killing hundreds of people and prompting tens of thousands to flee to safety.
The regime has kept up its offensive despite a UN Security Council resolution in February condemning such strikes.
And east of Damascus, regime troops backed by Lebanese Hezbollah fighters made fresh gains against rebel forces by taking the village of Hteitet Jarash, the Observatory said.
The village is near Mleiha, a former rebel bastion that fell to government control in mid-August after several months of fierce fighting and near-daily bombardment.