Around 300 civilians were killed in eleven airstrikes conducted by the US-led coalition in Syria, which Amnesty International investigated for its latest report. Amnesty says the US must come clean about the civilian toll of its fight against Islamic State.

Amnesty suspects that US Central Command (CENTCOM), which directs coalition airstrikes in Syria, “may have… carried out unlawful attacks” in Syria, failing to take necessary measures to prevent civilian killings.

“We fear the US-led coalition is significantly underestimating the harm caused to civilians in its operations in Syria,” said Lynn Maalouf, Deputy Director for Research at Amnesty International’s Beirut regional office.

“It’s high time the US authorities came clean about the full extent of the civilian damage caused by coalition attacks in Syria. Independent and impartial investigations must be carried out into any potential violations of international humanitarian law and the findings should be made public.”

Amnesty investigated evidence, including eyewitness accounts, reports by human rights organizations and the media, photographs and video footage as well as satellite imagery, related to 11 suspected coalition attacks in Syria. The group estimates that the attacks have claimed as many as 300 civilian lives. So far none of these deaths has been acknowledged by CENTCOM.

The report published on Wednesday added that the total civilian death toll from coalition action “could be as high as 600 or more than 1,000” since the operation against Islamic State (IS, formerly ISIS, ISIL) started in Syria in 2014.

One of the strikes investigated by Amnesty took place in the early hours of December 7, 2015. The attacks hit two houses in the village of Ayn al-Khan, near al-Hawl in al-Hasakah governorate in northern Syria, killing 40 civilians, including 19 children, and injuring at least 30 others, the report said.

According to an eyewitness account, an initial night strike was followed by a second attack from a helicopter gunship, which hit first responders trying to dig out survivors.

“At this point I had a two-month-old baby boy in my arms whom I had rescued. The hit caused me to fall and drop him… I fell into the hole made by the air strike. That was what saved me… My mother, aunt, wife and children – a daughter who was four years old and a son who was two and a half were all killed. The woman and her son who I’d rescued were killed. Everyone but me was killed,” the survivor said.

The strike is believed to have targeted IS fighters. But local Kurdish militia reportedly warned the coalition that there were civilians in the area.

Amnesty said CENTCOM’s failure to acknowledge civilian deaths in Syria, as well as the poor record of investigating such incidents in Afghanistan and Iraq, poses grave concerns over the toll which the civilian population of Mosul, Iraq is likely to face from the ongoing operation to take the city from IS. The US-led coalition is providing air support for the offensive.

“Given the likely increase in air strikes by the US-led Coalition as part of the Iraqi offensive to recapture Mosul, it is even more pressing that CENTCOM be fully transparent about the impact of their military actions on civilians. And it is crucial that they adhere scrupulously to international humanitarian law, including by taking all feasible precautions to spare civilians and to minimize harm to civilian homes and infrastructure,” said Maalouf.

A similar operation to capture Manbij, Syria, which is far smaller than Mosul, killed more than 200 civilians, Amnesty estimated.

Last week, Amnesty International blasted Russia for civilian deaths in Aleppo. The Syrian city is divided between government forces and various armed groups, including the Al-Qaeda offshoot Al-Nusra Front. Russia says that the militants use civilians as human shields and would not allow them to leave the city, derailing several attempts by Russia to open humanitarian corridors out of the city.