Gaza City  - Hamas admitted Friday that its own militants were behind a huge explosion in the northern Gaza town of Beit Lahiya that had killed eight Palestinians, including a four-month-old baby.

The radical Islamic movement ruling Gaza had initially said the early Thursday afternoon blast was caused by an Israeli air strike.

Militants in the Strip had responded by launching a barrage of more than 40 rockets and mortars at southern Israel.

Hamas' armed wing, the al-Qassam Brigades, issued a statement Friday, saying the blast was an accident, caused by the premature detonation of an explosive device being prepared by Hamas militants in the house for use in an "important" attack against Israel.

"The martyrs who went to heaven on Thursday at the Beit Lahiya house explosion died while they were making the final preparations on their way to carry out an important special Jihad operation," the statement said.

The massive explosion had reduced the two-storey house of senior Hamas commander Ahmed Hamoudeh to rubble and was heard throughout northern Gaza.

The Hamas statement said six of the dead were members of the al- Qassam Brigades, including three field commanders.

Four-month-old Nour Hamoudeh, the daughter of Majdi Adel Hamoudeh, one of the dead field commanders, and another, 22-year-old relative who was not an al-Qassam militant, were also killed.

Ahmed Hamoudeh, the owner of the house, is said to be a senior explosive expert for Hamas. He also once ran in municipal elections and won a seat in his town's municipal council.

An Israeli military spokeswoman said militants fired 22 mortar shells and 21 rockets, among them three Iranian-made, Russian type Grads at Israel at Israel Thursday, most of them after the Beit Lahiya blast. The projectiles caused massive damage and several injuries.

Four more rockets and mortars landed in Israel Friday.

The latest violence comes after Israeli Prime Minister Ehud Olmert's inner security cabinet decided earlier this week to give Egyptian efforts to broker a truce in Gaza another chance, and to put off a large-scale military invasion of the Strip.

The forum of some 12 senior ministers, however, also instructed the Israeli military to continue preparations for such a large-scale invasion, in case the truce talks failed. (dpa)