BAGHDAD >> A recent spike in civilian casualties in Mosul suggests the U.S.-led coalition is not taking adequate precautions to prevent civilian deaths as it battles the Islamic State militant group alongside Iraqi ground forces, Amnesty International said Tuesday.

The human rights group’s report follows acknowledgement from the coalition that the U.S. military was behind a March 17 strike in a western Mosul neighborhood that residents have said killed more than a hundred civilians. U.S. officials did not confirm there were civilian casualties but opened an investigation.

The report also cites a second strike on Saturday that it said killed “up to 150 people.” The U.S.-led coalition said in a statement that it was investigating multiple strikes in western Mosul that allegedly resulted in civilian deaths.

Evidence gathered on the ground in Mosul “points to an alarming pattern of U.S.-led coalition airstrikes which have destroyed whole houses with entire families inside,” the report stated.

It said any failure to take precautions to prevent civilian casualties would be “in flagrant violation of international humanitarian law.”

Iraqi forces began the assault on IS-held Mosul in October after months of preparation and buildup. In January, Iraq declared east Mosul “fully liberated” and government forces are now battling to retake the city’s western half.

Civilians, humanitarian groups and monitoring officials have repeatedly warned of the possibility of increased civilian casualties in western Mosul due to the higher density of the population and the increased reliance on airstrikes and artillery. Faced with their toughest fight against IS yet, Iraqi and coalition forces have increasingly turned to airstrikes and artillery to clear and hold territory in Mosul’s west.

Unlike its previous past fights against IS, Iraq’s government made the decision to instruct Mosul civilians to remain in their homes. In the battles for Fallujah and Ramadi, those cities were entirely emptied of their civilian population as Iraqi forces battled IS. In Mosul, the Iraqi government said it asked civilians to remain in place to prevent large-scale displacement.

When the operation to retake Mosul was launched, more than a million people were estimated to still be living in Mosul. Today, the United Nations estimates about 400,000 people remain trapped in IS-held neighborhoods in the city.

Amnesty International’s report quoted survivors and eyewitnesses of airstrikes that have killed civilians as saying “they did not try to flee as the battle got underway because they received repeated instructions from the Iraqi authorities to remain in their homes.”