At least 40 were wounded, 25 of whom were transferred to the Nasser Hospital in southern Gaza with severe burns, authorities at the Al-Aqsa hospital said.
Secondary explosions were heard and filmed, but it was not clear if they were caused by fuel tanks or munitions.
The Israel Defense Forces (IDF) said it had conducted a “precise strike” on a Hamas command and control centre embedded within a compound that previously served as the Al-Aqsa hospital.
“[The compound] was used by Hamas terrorists to plan and execute terrorist attacks against IDF troops and the state of Israel,” the military said.
It insisted that it had taken numerous steps to mitigate the risk of harming civilians, including the use of precise munitions, aerial surveillance and additional intelligence.