Tuesday's air strike in Jabalia caused a huge explosion that destroyed several residential buildings in the centre of the refugee camp, where before the war 116,000 people were living in an area of just 1.4 sq km (0.5 sq miles).
Jabalia resident Ragheb Aqal said it had felt like there was "an earthquake".
"I went and saw the destruction... homes buried under the rubble and body parts and martyrs and wounded in huge numbers," he told AFP news agency.
Video footage and photos showed hundreds of people searching the wreckage afterwards. "We're filling bags with children," cried one man, holding up a small white cloth bag covered in blood.
AFP reported that its video footage from the scene showed at least 47 bodies being pulled from the rubble.
A long line of body bags were laid outside the Indonesian Hospital, in nearby Beit Lahia. Its surgical director told the BBC's International editor Jeremy Bowen that it received 400 casualties, including 120 dead, and that the majority were children and women.