"The Hamas terrorist organization carried out a blatant violation of the ceasefire agreement, during which terrorists attacked IDF troops deployed in the Rafah area," the Israel Defense Forces said in a statement.
Israeli Prime Minister Benjamin Netanyahu had vowed to "respond accordingly".
Witnesses said the initial strike had targeted a tent inside the al-Mawasi displacement area, followed by blasts near the Kuwait hospital, prompting panic among families sheltering nearby.
Hamas called Israel's action barbaric, indiscriminate and a violation of the ceasefire which began on 10 October.
The Israeli military launched its offensive in Gaza in response to the Hamas-led attack on southern Israel on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.
More than 70,100 Palestinians have since been killed as a result of Israel's campaign, according to the territory's Hamas-run health ministry.