Beirut, Geneva: Air strikes since Thursday evening have killed more than 100 people including children and other family members of Daesh terrorists in Al Mayadin, a town held by the terrorists near Deir Al Zor in eastern Syria, a war monitor reported.

The Britain-based Syrian Observatory for Human Rights said the raids were carried out by US-led coalition warplanes.

A spokesman for the US-led coalition fighting Daesh said that its forces had conducted strikes near Al Mayadin on May 25 and 26 and were assessing the results.

The Observatory said more than 40 children were among those killed in the strikes, which levelled Al Mayadin’s municipality building.

Many of the families had fled from Raqqa, Daesh’s stronghold to the northwest, which US-backed Syrian Kurdish and Arab fighters are pushing towards in an offensive against the terrorists, the Observatory said.

Residents saw reconnaissance aircraft and warplanes circling the city at 7:25pm before they fired missiles which struck two buildings, one of which was a four-storey block housing Syrian and Moroccan families of Daesh fighters.

More strikes took place after midnight.

Daesh is losing ground in both Syria and Iraq under assault from an array of sometimes rival forces in both countries. Many of its fighters who have retreated from other fronts are massing in Syria’s Euphrates basin area.

The US-led coalition says it is careful to avoid civilian casualties in air strikes and investigates any that are reported to have taken place.

Meanwhile, the UN human rights chief called on all air forces operating in Syria on Friday to take greater care to distinguish between legitimate military targets and civilians in their escalating air strikes especially in the northeast against Daesh.

“The rising toll of civilian deaths and injuries already caused by air strikes in Deir Al Zor and Al Raqqa suggests that insufficient precautions may have been taken in the attacks,” UN High Commissioner for Human Rights Zeid Ra’ad Al Hussain said in a statement.

His spokesman Rupert Colville told a Geneva briefing: “There are multiple air forces operating in this part of Syria including the US-led coalition. We also understand that there are Iraqi aeroplanes as well.”