(Reuters) - At least 15 people were killed and many wounded on Thursday when Israeli forces shelled a U.N.-run school sheltering Palestinian refugees in northern Gaza, said a spokesman for the Gaza health ministry, Ashraf al-Qidra.
The director of a local hospital said various medical centres around Beit Hanoun were receiving the wounded.
"Such a massacre requires more than one hospital to deal with it," said Ayman Hamdan, director of the Beit Hanoun hospital.
A Reuters photographer at the scene said pools of blood had collected on the ground and on student desks in the courtyard of the school near the apparent impact mark of the shell.
Scores of crying families who had been living in the school ran with their children to the hospital where the victims were being treated a few hundred meters away.
Laila Al-Shinbari, a woman who was at school when it was shelled, told Reuters families had gathered in the courtyard expecting to be evacuated shortly in a Red Cross convoy.
"All of us sat in one place when suddenly four shells landed on our heads ... Bodies were on the ground, (there was) blood and screams. My son is dead and all my relatives are wounded including my other kids," she wept.
Chris Gunness, spokesman for the main U.N. agency in Gaza UNRWA, confirmed the strike and criticised Israel.
"Precise co-ordinates of the UNRWA shelter in Beit Hanoun had been formally given to the Israeli army ... Over the course of the day UNRWA tried to coordinate with the Israeli Army a window for civilians to leave and it was never granted," Gunness said on his Twitter page.
Earlier on Thursday, Gunness told Reuters that Israeli forces had bombed U.N. shelters on three separate occasions since Monday, in incidents which did not cause injuries.
The Israel army had no immediate comment on the reports.