Twenty members of the Islamic State (IS) were killed in Syrian air force raids Wednesday against the jihadists' bastion in Raqa, the Syrian Observatory for Human Rights said.
The report comes after Syrian rebels killed at least 14 people, among them women, among them women, in the village of Khatab in the central province of Hama overnight, state media and the Observatory said.
"At least 20 members of IS were killed and others were injured in air strikes... targeting an IS training base in Raqa," the Observatory said.
The strikes also destroyed 14 IS military vehicles, the Observatory added.
On June 29, IS declared the establishment of a "caliphate," referring to an Islamic system of rule that was abolished nearly 100 years ago.
Its jihadists are firmly in control of Raqa and have secured large swathes of territory in eastern Syria and in neighbouring Iraq.
While some rebels initially welcomed the IS -- then known as the Islamic State of Iraq and the Levant (ISIL) -- as a potential ally, its abuses and quest for control turned them against it.
Rebels have been fighting IS since January.
For its part, Syrian President Bashar al-Assad's regime has escalated its attacks against IS positions since the group launched a Sunni militant offensive in neighbouring Iraq a month ago.
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Syrian Kurds have been fighting IS since 2013.
On Wednesday, a Tunisian jihadist carried out a suicide car bomb attack in the Kurdish town of Ain Eissa, killing four Kurdish fighters.
In the northern province of Aleppo, IS seized three Kurdish areas to the east of Ain al-Arab (Kobani in Kurdish) after two days of fighting that killed at least 22 jihadists and 18 Kurdish fighters, said the Observatory.
The reports come hours after Syrian state television said rebels carried out a "massacre" that included women and children, while the Observatory said seven men and seven women had been "executed" by rebel fighters.
The Observatory said the rebels accused the residents of Khatab village of "collaboration with the criminal regime", and executed the 14.
Meanwhile, in the city of Aleppo, four people, among them a media activist, were killed and dozens more wounded in air raids on rebel-held areas, the Observatory said.
Aleppo has been under a massive aerial offensive since December.
According to the Observatory, by May some 2,000 civilians including 500 children had been killed in the daily air strikes.
Rights groups have condemned as a "war crime" for failing to discriminate between military and civilian targets.
Rebel fighters also fired mortars at regime-held areas of divided Aleppo, killing three people, according to the Observatory.
More than 162,000 people have been killed since Syria's conflict erupted in March 2011.