The US military has admitted carrying out airstrikes that killed dozens of troops loyal to Syrian President Bashar al-Assad in eastern Syria earlier this year. The US-led coalition said the "mistake" on 17 September came as it attempted to target Islamic State (Isis) positions.

Coalition aircraft instead killed members of the Syrian forces fighting the Islamic extremists in the attack near Deir Ez-Zor, or Deir al-Zour, near the border with Iraq, which broke a ceasefire in hostilities in the country . The aircraft involved in the attack were said to be from the UK, US, Denmark and Australia.

Assad, along with Russian officials, has maintained that the deadly airstrikes were intentional. According to reports, the attack was only halted when Russia informed the US they were striking the wrong positions.

Although no official death count has been produced, Russia said that the coalition air strike killed 62 Syrian soldiers and more than 100 were wounded. And the Britain-based Syrian Observatory for Human Rights (SOHR) put the death toll at 83.

US Air Force Brigadier General Richard Coe, the investigating officer, said they could only identify 15 dead regime loyalists but conceded that the death toll was likely to be higher. He said, according to the Guardian: "We made an unintentional, regrettable error, based on several factors in the targeting process." However, Coe added there had been "no intent to target Syrian [government] forces".

"In this instance, we did not rise to the high standard we hold ourselves to, and we must do better than this," said US Lieutenant-General Jeff Harrigian, according to the BBC.

The incident sparked a further diplomatic crisis between Washington and Assad, who said that he believed the militants were targeted on purpose. "It was four aeroplanes that kept attacking the position of the Syrian troops for nearly one hour, or a little bit more than one hour," he told the AP news agency.

A spokesman for the UK Ministry of Defence (MoD) said the report, published on Tuesday, showed the decision to carry out strikes near was "made in good faith". "We welcome the coalition's report and its conclusion that the decision to identify the targets as Daesh (IS) fighters was reasonable," he said. "We would not, and did not, intentionally strike known Syrian Regime military units".

Deir al-Zour
Men ride bicycles past a damaged mosque along a deserted street filled with debris in Deir ez-Zor Reuters