Thousands of Palestinians have taken part in a mass funeral for victims of an Israeli raid that left 14 dead in the Gaza Strip early on Sunday.
Some of the victims of the Gaza raids were young boys
Dozens of masked, gun-toting militants joined the mourners, who vowed to avenge the killings.
Israel said the raids into the al-Bureij and Nusseirat refugee camps had targeted Palestinian radicals.
The dead included 10 militants and three boys under 16 years old. Almost 100 people were wounded.
Ismail Haniya, a leader of the militant group Hamas, said the killings would "not pass without punishment".
"This massacre will only make our people stronger and more determined to continue our resistance," he told AFP news agency.
Israeli tanks supported by attack helicopters first moved into the camps under cover of darkness.
The battled raged for several hours, as armed Palestinians took to the streets to confront the incoming force.
The Israelis say their troops were met by anti-tank missiles, rocket-propelled grenades and heavy gunfire.
"This is a pinpoint operation against the terrorist infrastructure in the central Gaza Strip," the Israeli army said.
The army said the incursion had been launched to target militants who had attacked nearby Jewish settlements recently.
Most of the militants killed belonged to Hamas, a group which has killed scores of Israelis in suicide bombings and ambushes.
There were no Israeli casualties reported, and the army has now withdrawn.
Palestinian Cabinet minister Saeb Erekat hit out at Sunday's raid.
"At a time when they're speaking about withdrawing from Gaza, they're destroying Gaza," Mr Erekat said, referring to Israeli Prime Minister Ariel Sharon's plan to evacuate Jewish settlers from the Gaza Strip.
The BBC's James Rogers in Gaza says Israel wants to try and weaken Palestinians militants as much as possible before the planned withdrawal.
But Israeli government spokesman Avi Pazner said the operation had "nothing to do with any future plan about Gaza".
"Terrorism is pouring out of this refugee camp [al-Bureij], and we have to stop it," Mr Pazner said.
"We believe that by doing so we have prevented acts of terror in Israel and saved many human lives."
The raids came less than a day after a failed Palestinian attack on the main crossing point between the Gaza Strip and Israel.
Up to six Palestinians were killed and about 20 wounded.
Palestinian witnesses say two jeeps disguised as Israeli military vehicles drove up to Erez crossing point.
One exploded near a Palestinian checkpoint, killing the driver and two Palestinian police. The other reached the Israeli position before exploding.
An Israeli army spokesman described the blast as a suicide bomb that went off prematurely. There were no Israeli casualties.
The militant groups Hamas, Islamic Jihad, and the al-Aqsa Martyrs Brigades, say they carried out the attack, calling it a joint "self-sacrifice operation".