A mother and four children were among the dead and at least 24 people were wounded, hospital officials said.
A spokesman for Iz al-Din al-Qassam, Hamas' military wing, denied Def had been wounded. Abu Ubaida, a spokesman for the Qassam brigades, said: "This is totally incorrect. We deny it. We deny it completely. This is only a cover-up for the massacre of Palestinian civilians committed by the Zionist enemy."