"The family was hit during the explosion of the second missile that ignited secondary explosions or from objects that flew towards them because of the force of the blast," the army said in a statement on the conclusions of the full investigation.

The military also released aerial footage of Monday's incident in the town of Beit Hanun in the north of the Hamas-ruled Gaza Strip, which showed several large explosions which the army said were secondary detonations.

According to the statement, an Israeli aircraft fired a first missile at four militants it identified as "carrying backpacks loaded with ammunition."

One gunman was hit in the strike, which was followed by a strong secondary explosion.

"Immediately after the explosion a second gunman was targeted and hit as well, causing an even bigger explosion.

"Both explosions were significantly stronger than those caused by the IDF attacks against them," the Israel Defence Forces statement said.

On Wednesday the Israeli human rights group B'Tselem said its own investigation cast doubt on the army's initial account of the killing of Meissar Abu Maateq and four of her children, aged one to five.

"The material (B'Tselem) has collected, including an analysis of the area, photographs of bodies, and eyewitness accounts, raise doubt about the IDF spokesperson's contention that a secondary explosion is what killed the family," the group said.

© 2008 Agence France-Presse