Syrian government warplanes pounded an Islamic State group stronghold as well as other towns controlled by the jihadis Sunday, conducting more than a dozen airstrikes and killing at least 11 people, activists said.
For more than a year, President Bashar Assad's air force rarely targeted territory controlled by the Islamic State group in northern Syria, instead focusing on mainstream rebel groups.
But government jets have begun hitting the extremists more regularly since the jihadis overran much of neighbouring northern and western Iraq in June.
Even in that context, the intensity of Sunday's air raids appeared unusually high, with at least 19 strikes hitting the group's stronghold of Raqqa in northeastern Syria, the Britain-based Syrian Observatory for Human Rights said.
Observatory directory Rami Abdurrahman said six of those raids targeted a military court. He said at least 16 Islamic State members were killed in Raqqa, and around 40 wounded. He said there were an additional 22 civilian casualties, but he didn't have an exact breakdown of dead and wounded.
The Local Coordination Committees activist collective also reported the airstrikes on Raqqa, but put the death toll at 11. Differences in casualty figures are common in the immediate aftermath of attacks in Syria.
Both activist groups also reported government airstrikes on Islamic State-controlled areas in Aleppo province as well, including the towns of Akhtarin and Dabiq.
Both communities were among around a dozen towns and villages fighters from the extremist group overran last week.
Those gains have jeopardised the mainstream rebels' position in Aleppo province as well as the city of Aleppo itself, where opposition fighters are also under assault by government troops.
With the rebels control over half of Aleppo looking increasingly precarious, the main Western-backed opposition group called Saturday for US airstrikes against the Islamic State to help the mainstream rebels.
The Coalition has long appealed for more robust military support from the West to help in its fight to oust Assad, and more recently to counter the rise of Islamic extremists.
The group's latest appeal appeared aimed at capitalising on the recent US aerial intervention in neighbouring Iraq, where American military aircraft have targeted the Islamic State group.
But President Barack Obama has long refused demands for similar action in Syria, fearing it could draw the US into an increasingly complex and bloody civil war.