A United Nations probe into charges of human rights violations says Syrian forces have committed “crimes against humanity” during the government’s crackdown against protesters. The commission on Monday called for Syria to immediately end the violence and investigate and prosecute those who committed it. The U.N. Human Rights Council set up the commission in August. It presented its first report Monday at a news conference in Geneva.

Investigators gathered evidence from at least 223 victims and witnesses from the end of September through mid-November. The commission concluded that the army and security forces seriously breached international law.