United Nations Secretary-General Antonio Guterres was "horrified" by the deadly strike on a hospital in Gaza that left at least 200 people dead, he said in a social media post Tuesday.

"My heart is with the families of the victims. Hospitals and medical personnel are protected under international humanitarian law," Guterres said in the message on X, formerly Twitter.

In a statement released shortly after by his spokesman, Guterres also condemned an attack on a school run by the UN in a Gaza refugee camp that killed six people.

The Palestinian militant group Hamas has blamed Israel for the hospital strike. Israel has said it was caused by a rocket misfired by Islamic Jihad militants in Gaza.