US airstrike on Syria mosque 'violated international law'

US military forces violated international humanitarian law in an attack on a mosque in Syria earlier this year, UN investigators said on Wednesday, failing to take all possible precautions to avoid civilian deaths.

On March 16, a series of US airstrikes on a mosque compound killed 42 civilians in the village of al-Jinah in the Aleppo province.

US officials initially denied that a mosque was targeted, stating that the airstrikes had struck "an al-Qaeda in Syria meeting location" and had killed "dozens of core al-Qaeda terrorists".

A new report by the UN Commission of Inquiry (COI) on Syria contradicts claims made by the US coalition, saying US forces did not do enough to verify the targets of the strike and have released no information proving an al-Qaeda meeting was taking place.

All of those killed in the strikes were civilians, including one woman and five boys aged between six and thirteen years old.

"The Commission therefore concludes that United States forces failed to take all feasible precautions to avoid or minimize incidental loss of civilian life, injury to civilians and damage to civilian objects, in violation of international humanitarian law," the report said.

Mosques are protected objects under international humanitarian law and may not be the object of attack unless they are being used for military purposes, the report added.

Survivors of the attack told UN investigators that the gathering at the mosque was "strictly religious", with most attendees al-Jinah residents or internally displaced persons from neighbouring towns.

The US targeting team had information on the target three days prior to the airstrike but did not undertake additional verification of target activities, which would have been expected if the site was known to be a mosque.

"The Commission is gravely concerned about the impact of international coalition air strikes on civilians", the COI report says.

"In Al-Jinah, Aleppo, forces of the United States of America failed to take all feasible precautions to protect civilians and civilian objects when attacking a mosque".

The US-led coalition, which operates in both Syria and neighbouring Iraq, says it takes all possible measures to avoid civilian casualties.

In August, it acknowledged the deaths of 624 civilians in its strikes in Syria and Iraq since 2014, but rights groups say the number is much higher.