The Palestinian police chief, Ghazi Jabali, said members of the hardline Islamic Resistance Movement (Hamas) were responsible for the blast that wrecked a three-storey building in the heart of Gaza City.
Palestinian police found 30 kilograms (70 pounds) of explosive powder, 70 litres of explosive liquid, a 10-kilo bomb, six missiles and dozens of homemade rockets in the apartment - and an Uzi sub-machine-gun, two assault rifles and 150 greandes.
The explosion killed Kamal Kheil, 28, a leader of Ezzedin al-Kassam, the Hamas armed wing, four of his colleagues and a four-year-old boy. Many people were wounded.
It scattered human remains in a radius of up to 100m. "I saw heads and organs flung through the air," said Jamal al-Assali, 25, who lives in the Sheikh Radwan district, a Hamas stronghold.
Hatem Abu Kaied heard "a colossal noise which terrified everybody". There were "blown-up bodies and corpses, including a baby. It was terrible."
Mr Jabali said the whole neighbourhood could have been blown up if police had not arrived quickly and neutralised the rest of the explosives by dousing them with water - sending up toxic fumes that injured 40 people.
Kheil was on Israel's most-wanted list for the killing in 1993 of Lieutenant- Colonel Meir Mintz, the highest ranking Israeli killed during its occupation of Gaza. He was suspected of involvement in the killing of at least 16 Palestinian collaborators. The Palestinian Authority wanted to question him in connection with the deaths of three other Palestinians, killed since self-rule began in May.
In an effort to derail the Israel-PLO accord, Hamas has carried out a series of suicide attacks, including a Tel Aviv bus bombing in October in which 22 people died. It blamed yesterday's explosion on Israel and the PLO, threatening "swift and painful retaliation''. Palestinian journalists who knew Kheil said that he wore an explosive-laden belt which he vowed to set off if in danger of capture.
Photograph, page 13