A senior commander of the Palestinian Islamic Jihad movement was among at least five people killed and 40 wounded in an explosion in the Gaza Strip late today, a group spokesman and local medics said.
The spokesman accused Israel of mounting an air strike that destroyed a house and vowed revenge for the death of Ayman Fayed, better know as Abu Abdallah.
However, an Israeli military spokeswoman said she was aware of no such action.
Israeli ministers said this month they may step up efforts to kill senior Gaza militant leaders. Israeli forces have carried out a number of air strikes on Gaza militants in cars lately, but not since 2006 have they bombed a house.
"We will respond to this Zionist massacre painfully," Abu Ahmed, a spokesman for Islamic Jihad's armed wing said.
"We will strike the enemy everywhere."
Among the wounded was Fayed's wife, he added.
Medics said at least 40 people had been wounded in the explosion at the al-Bureij refugee camp.
The Gaza Strip is ruled by Islamist Hamas, which seized the coastal enclave in June from Palestinian President Mahmoud Abbas's secular Fatah. Islamic Jihad operates in a loose alliance in Gaza with Hamas.