An Israeli air strike on the Gaza City home of a member of the Palestinian militant group Hamas has killed nine members of the same family.
The force of the air strike completely destroyed the house
A couple and their seven children died in the attack. Among the injured was the leader of Hamas's military wing.
At least 14 other Palestinians died in military action as Israeli troops occupied positions in central Gaza.
More than 60 have been killed since militants captured an Israeli soldier in a cross-border raid two weeks ago.
The Israeli military said the overnight bombing targeted Hamas military commander Muhammad Deif - who has been on its wanted list for a decade.
Hamas denied that he was in the house at the time, but the BBC has learnt that he was in fact injured in the attack.
Security officials quoted by the Associated Press news agency said he underwent four hours of spinal surgery, and could end up paralysed.
The house in Gaza City was destroyed by a 250kg (550-pound) bomb dropped by an F-16 jet, according to Israeli military sources.
Local officials said the building belonged to Hamas activist Nabil Abu Salmiyeh, a lecturer at Gaza City's Islamic University, and that he, his wife and seven of their nine children were killed.
Hospital officials said 37 people were wounded in the attack, three of them seriously.
The attack happened as Israeli troops entered a few hundred metres into farmland east of Khan Younis in central Gaza.
Several deadly clashes followed the incursion:
- A Palestinian youth was killed by an Israeli tank shell east of Deir al-Balah
- Two armed Palestinians were killed in an explosion
- A Palestinian policeman and a militant were shot dead in clashes with troops
- Five Palestinians died in a missile attack near Deir al-Balah. Israel said the victims were armed gunmen but a local security source said they were unarmed teenagers.
Israel said leaders of the Hamas military wing had been meeting in the house that was destroyed in Gaza City, and accused the militants of using civilians as a shield.
"Israel is compelled to take action against those planning to unleash lethal terror attacks against Israeli citizens," said David Baker, an official in the office of Israeli Prime Minister Ehud Olmert.
"Palestinian terrorist leaders continue to take refuge amongst and hide behind their own civilians."
Abu Obeideh, a spokesman for Hamas's military wing, vowed revenge.
"We will make the leaders of the Zionist regime regret this Nazi crime," he said.
Israeli forces have attempted to kill Mr Deif a number of times and there have been reports of him being wounded in the past.
The Israelis say he is a master bomb-maker who has been behind numerous suicide bomb attacks in Israel.
'No prisoner deal'
About 65 Palestinians and one Israeli have died since Cpl Gilad Shalit, 19, was seized at a border post.
Most of the dead have been Palestinian militants, but civilians have also died under Israeli fire and air strikes.
Israel says the offensive is designed to free the captured soldier and end rocket attacks on southern Israel by Palestinian militants.
Exiled Hamas leader Khaled Meshaal, along with the militants who seized Cpl Shalit, have been insisting that the soldier only be handed over in exchange for Palestinian prisoners held in Israeli jails.
However, Mr Olmert has ruled out any negotiations with the Hamas-led Palestinian government, calling the militant group a "terrorist bloody organisation".
There are warnings that the military crisis could trigger a major humanitarian problem in Gaza.