Intensified airstrikes on IS-held areas in Raqqa kill dozens

This undated file image posted on a militant website Jan. 14, 2014 shows fighters from the al-Qaida linked Islamic State of Iraq and the Levant (ISIL) marching through Raqqa, Syria. (AP Photo/Militant Website)

(ABC News) — Syrian opposition activists are reporting that airstrikes on parts of the northern city of Raqqa that are controlled by the Islamic State group have intensified, killing at least 29 people in the past two days.

The U.S.-backed Syrian Democratic Forces have been trying to capture the city since launching an offensive on June 6 under, backed by airstrikes by the U.S.-led coalition. The Kurdish-led force now controls half the city.

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Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said on Wednesday that the airstrikes have intensified over the past days, ahead of a possible new push on Raqqa.

The Observatory says 29 civilians, including nine women and 12 children, were killed on Tuesday alone.

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Sound and Picture Organization, which documents IS violations, says 43 have been killed.