By Rushdi Abualouf and Tom McArthur, BBC News
At least 71 Palestinians have been killed in an Israeli air strike, that hit a densely populated area of displaced people in the al-Mawasi area of Khan Younis in Gaza, the Hamas-run health ministry says.
The Israeli military had designated this area as a safe zone, urging Palestinians to seek shelter there.
More than 289 people were injured in the strike, according to the health ministry's statement.
The Israeli military said it was looking into the incident. Israeli media is reporting that senior Hamas leader Mohammed Deif was a target of the attack.
An eyewitness told the BBC that the site of the strike looked like an "earthquake" had hit, and videos from the area show smouldering wreckage and bloodied casualties being loaded onto stretchers.
People can be seen trying desperately to pick through the rubble of a large crater with their hands.
Footage from the nearby Kuwait field hospital revealed chaos with patients being treated on the floor.
A Hamas official, cited by Reuters, called the attack a "grave escalation" that showed Israel was not interested in reaching a ceasefire agreement.
- Reuters