BEIRUT (Reuters) - Bombing runs by the Syrian air force over the past 10 days have killed at least 221 civilians, a third of them children, a group monitoring Syria’s civil war said on Thursday.

The intensifying offensive by President Bashar al-Assad’s forces has heightened concerns among his opponents that he may be taking advantage of U.S.-led air raids on Islamic State insurgents to regain territory elsewhere in the country.

Since Oct. 20 the Syrian military has staged at least 769 attacks including barrel bombings in many areas of Syria, according to the Britain-based Syrian Observatory for Human Rights, and more than 500 people have been wounded.

It said the strikes targeted the eastern province of Deir al-Zor, Homs in central Syria as well as contested provinces in the more populated west such as Latakia, Quneitra, Hama, Aleppo, Idlib and Deraa, as well as the fringes of Damascus.

“The Syrian Observatory for Human Rights renews its condemnation at the continued silence of the international community regarding the massacres committed daily by the regime of Bashar al-Assad against the sons of the Syrian people.”

The Syrian armed forces have sharply increased the number of raids since a U.S.-led coalition of Western and Arab states began bombing Islamic State forces in the country last month.

Damascus has not raised objections to the selective air strikes, which have concentrated on the insurgent-dominated east and north of Syria, far from the most populous areas near the capital and the Mediterranean coast.

The United States says it has no wish to bolster Assad with its aerial campaign against Islamic State, an al Qaeda offshoot.

But Western and regional powers were driven into action by international alarm over Islamic State’s advances across large expanses of Syria and adjacent Iraq, its declaration of a caliphate bent on remaking Middle East borders and its massacres of Shi’ite Muslims, Christians and other minorities who do not share its hardline, puritanical brand of Sunni Islam.