The Hamas-run health ministry in Gaza says 141 Palestinians have been killed in Israeli air strikes since Saturday.
About 400 people have been injured, according to the health ministry’s statement.
One of the air strikes hit a designated humanitarian zone in the al-Mawasi area near Khan Younis.
Israeli Prime Minister Benjamin Netanyahu said the attack was targeting senior Hamas leader Mohammed Deif, but there was “no certainty” that he had been killed.
An eyewitness in al-Mawasi told the BBC that it looked like an “earthquake” had hit.
Videos from the area show smouldering wreckage and bloodied casualties being loaded on to stretchers.
BBC Verify has analysed footage of the aftermath of the strike, confirming that it took place within an area shown on the Israel Defense Forces (IDF) website as a humanitarian zone.
Gaza’s Hamas-run civil defence agency said that 17 people had been killed in a second Israeli strike on Saturday.
The attack is said to have targeted a prayer hall in the Shati refugee camp to the west of Gaza City. The Israeli military has not yet commented on the claim.
A Hamas official, cited by Reuters, called the attacks a “grave escalation” that showed Israel was not interested in reaching a ceasefire agreement.
The ceasefire negotiations being held in Qatar and Egypt ended on Friday without success, the BBC understands.
