Three Palestinian children have been killed after an Israeli tank shell hit northern Gaza, Palestinian doctors say.
Israel's military confirmed it launched an attack, saying it had targeted people setting up a rocket launcher.
Doctors said two boys aged 10 and 12 died of shrapnel wounds. A 12-year-old girl who was critically injured in the blast died also in hospital.
The Israeli army expressed sorrow for the deaths of the children, but said it held militant groups responsible.
"We identified and fired at several rocket launchers aimed at Israel in the Beit Hanoun industrial zone," an Israeli army spokeswoman said.
"We also identified several suspicious looking people fiddling with the rocket launchers before we fired. The army regrets terror organisations' cynical use of children," she added.
Palestinian health officials told news agencies the two boys were cousins Mahmoud Ghazal, 10, and Yehiya Ghazal, aged 12.
The girl was named as Sara Ghazal, 10, another cousin.
The area around Beit Hanoun is frequently used by Palestinian militants to launch rocket attacks against southern Israel.
According to Palestinian medical officials, eight children have now been killed by Israeli military operations in Gaza and the West Bank in just over a week.