U.S.-led coalition air strikes have killed at least 224 civilians since the Syrian forces it backs entered Islamic State group bastion Raqa a month ago, a monitor said on Thursday, July 6, according to AFP.

Arab and Kurdish fighters from the Syrian Democratic Forces broke into Raqa on June 6 after a months-long operation to encircle the northern city.

"At least 224 civilians, including 38 children and 28 women, have been killed in air strikes by the global coalition on Raqa since the SDF entered it," said the Syrian Observatory for Human Rights.

The Britain-based Observatory said it did not have a toll for civilians killed in other ways, including by other military operations, mines, or while trying to flee the city.

Tens of thousands of civilians are believed to be trapped inside Raqa, with warnings that the jihadists are using them as human shields.

Many Raqa residents who have managed to escape say IS snipers are targeting anyone trying to leave the city.

The Observatory said clashes and air strikes in Raqa had killed 311 IS jihadists and 106 SDF militiamen since June 6.

The U.S.-backed coalition is providing the SDF's campaign on Raqa with heavy air support, as well as special forces advisers, weapons, and equipment.

Since IS captured Raqa in early 2014, it has served as the de facto capital of the jihadist group's Syrian territory.