The US recently spurned a call by the UN to temporarily halt airstrikes on the Syrian city of Raqqa to allow civilians to flee. That call had come after multiple instances of US strikes killing civilians in and around the city.

Today, UN officials are warning that the city’s population is paying an “unacceptable price” from the US airstrikes, and that continued US bombardment may be in violation of international law as a result. The US has been trying to back an invasion of Raqqa against ISIS.

An estimated 20,000 civilians remain in Raqqa, and the US has labeled them “human shields.” The UN High Commissioner for Human Rights warned that in just the month of August they’d documented 151 civilian deaths from the US-led invasion and US airstrikes.

The high commissioner noted that all civilians, including human shields, must be protected at all times, and said the attacking forces (which is to say, the US) are ignoring humanitarian law’s “principles of precautions, distinction, and proportionality.”

US officials have insisted they are taking utmost care to avoid civilian deaths. In reality, however, the Pentagon’s main effort in keeping the official death toll down has been to deliver preposterously low undercounts of how many they’ve killed in reports.