A senior militant from the Islamic Jihad movement is among at least seven people killed in an explosion in the Gaza Strip, which injured more than 40.
The Islamic Jihad commander's home was flattened by the blast
The blast destroyed the home of the commander, Ayman Fayed - known as Abu Abdallah - in the Bureij refugee camp in central Gaza.
An Islamic Jihad spokesman accused Israel of targeting the house in an air strike, and vowed revenge.
Israel said it had no knowledge of a raid being carried out on the area.
Officials from Hamas, the Islamist party which last year seized the Gaza Strip from the secular Fatah party of Palestinian President Mahmoud Abbas, said the cause of the blast was unclear.
The wife and two of Mr Fayed's children were killed in the blast, Palestinian medics said.
The death toll is expected to rise as there are reported to be people still trapped under the debris. Emergency services say the rescue operation will go on through the night.
Abu Ahmed, a spokesman for Islamic Jihad's armed wing, told Reuters news agency that the group would avenge "this Zionist massacre" and "strike the enemy everywhere".
Israel has been responding to rocket fire from Gaza with tough military action. In less than three months more than 150 Palestinians - mainly militants - have been killed.
Bureij is the smallest but most densely populated of eight refugee camps in the Gaza Strip.