The U.N. rights chief said Tuesday he was "appalled" by a deadly Israeli strike near a south Beirut hospital Monday, demanding a "prompt and thorough investigation."

"I am appalled by the Israeli strike near Rafik Hariri University Hospital in Beirut's densely populated Jnah neighborhood that reportedly killed at least 18 people, including four children, and wounded 60 others," Volker Turk said in a statement.

"The fundamental principles of international humanitarian law concerning the protection of civilians must be respected."