US air strike kills at least 80 civilians in Syria, as UN condemns rising death toll

A US-led coalition air strike on the eastern Syrian town of Mayadeen early on Friday killed at least 80 relatives of Islamic State group fighters, including 33 children, a monitoring group told AFP.

"The toll includes 33 children. They were families seeking refuge in the town's municipal building," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights. 

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

A separate air strike late on Thursday evening killed at least 35 civilians.

"The rising toll of civilian deaths and injuries already caused by air strikes in Deir Ezzor and Al-Raqqa suggests that insufficient precautions may have been taken in the attacks,” UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein said in a statement, stressing that extra caution should be taken in the campaign in the northeast against the Islamic State group. 

His spokesman Rupert Colville told a Geneva briefing: "There are multiple air forces operating in this part of Syria including the (US-led) coalition, mainly the coalition. We also understand that there are Iraqi airplanes as well."

"I can't begin to identify who is responsible," he added.

Air strikes in mid-May killed nearly two dozen farmworkers, most of them women, in a village in eastern Raqqa and at least 59 civilians in residential areas of Deir Ezzor, Zeid said.

A spokesman for the US-led coalition fighting Islamic State told Reuters that its forces had conducted strikes near Mayadeen on 25 and 26 May and were assessing the results.

The Thursday evening air strike in Mayadeen killed at least 35 civilians, including family members of Islamic State fighters, said the Observatory.

Most air raids against IS strongholds along the Euphrates basin in Syria have been conducted by a US-led coalition and by Syrian and Russian jets.

In two days, scores dead

Iraqi warplanes have also carried out at least one air raid in east Syria.

The deaths bring the total number of people killed in two days of aerial bombardment in Mayadeen to 115 said the monitor, the Britain-based Syrian Observatory for Human Rights,

Residents saw reconnaissance aircraft and warplanes circling the city at 7.25pm local time before they fired missiles which struck two buildings, one of which was a four-storey block housing Syrian and Moroccan families of Islamic State fighters.

Islamic State 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 amassing in Syria's Euphrates basin area.

Between 23 April and 23 May the Observatory reported that at least 225 civilians had been killed in strikes by the US-led coalition and 146 had been killed by Syrian government aircraft.

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. Russia and Syria's government both deny targeting civilians.

On Thursday, the US confirmed that one of its air strikes against IS in Mosul in March killed at least 105 civilians.