Syria activists say airstrikes on IS-held Raqqa kill 18

FILE - This file image posted on the Twitter page of Syria's al-Qaida-linked Nusra Front on Tuesday, June 14, 2016, which is consistent with AP reporting, shows Nusra Front fighters moving forward to fight against Syrian troops and pro-government gunmen at the hilltop of Khalsa village, southern Aleppo, Syria. The Syrian government has suffered serious setbacks in its campaign to retake the Islamic State's de facto capital of Raqqa, even with Russia's support. Arabic, bottom right, reads, "Jihadis on their way to Khalsa village." (Al-Nusra Front Twitter page via AP, File) (The Associated Press)

FILE - In this Saturday, June 18, 2016 file photo, Syrian President Bashar Assad shakes hands with Russian Defense Minister Sergei Shoigu in Damascus, Syria. The Syrian government has suffered serious setbacks in its campaign to retake the Islamic State's de facto capital of Raqqa, even with Russia's support. (Vadim Savitsky/ Russian Defense Ministry Press Service pool photo via AP, File) (The Associated Press)

FILE - In this Saturday, June 18, 2016 file photo, Russian fighter jets and bombers are parked at Hemeimeem air base in Syria. The Syrian government has suffered serious setbacks in its campaign to retake the Islamic State's de facto capital of Raqqa, even with Russia's support. (Vadim Savitsky/Russian Defense Ministry Press Service pool photo via AP, File) (The Associated Press)

Syrian activists say airstrikes on the Islamic State's de facto capital, Raqqa, have killed at least 18 civilians. The victims include two children, aged 10 and 15 years.

The activists are blaming Russian and Syrian air force for Wednesday's airstrikes. The U.S.-led coalition has also been bombing the IS bastion in Syria.

Activists from the group known as Raqqa Is Being Slaughtered Silently, which relies on residents to smuggle news out of IS-held territory, say the air raids also wounded 28 people.

The group says at least one airstrike targeted a neighborhood popular among "foreign fighters" — militants who have migrated to Syria to fight with the extremist IS group.

Another group, the Britain-based Syrian Observatory for Human Rights, says 25 civilians died in the airstrikes, among them six children.