An airstrike on Iran’s Evin prison containing political prisoners represents a grave violation of international humanitarian law, says the UN human rights office, Reuters reports.

“Evin prison is not a military objective, and targeting it constitutes a grave breach of international humanitarian law,” UN human rights spokesperson Thameen Al-Kheetan told reporters in Geneva on Tuesday, without naming Israel.

He said that his office has received reports of fires inside the facility and an unspecified number of injuries.