Israeli forces killed at least 49 Palestinians in a land and air blitz in the Gaza Strip on Saturday, medics said, amid warnings that the violence had "buried" the peace process.
It was the deadliest day since Israel's withdrawal from Gaza in the summer of 2005.
At least 13 civilians, seven of them women, were among the dead and more than 150 people were wounded, several of them critically, Dr Muawiya Hassanein, the head of Gaza emergency services, told AFP.
Two Israeli soldiers were also killed on Saturday in Gaza, and another seven soldiers, including one officer, were wounded, the army said.
Senior Palestinian negotiator Saeb Erakat said the Middle East peace talks formally revived in November at a US conference had been "buried" under the rubble of the Israeli incursion.
"The negotiations are buried under the houses that were destroyed in Gaza," Erakat told AFP. "The peace process has been destroyed because of the aggressions and the crimes that have been committed."
Israeli tanks supported by helicopters moved into the area in and around the crowded town and refugee camp of Jabaliya and nearby Tufah in northern Gaza just after midnight on Friday, witnesses said.
By midday troops had pushed nearly three kilometres inside the Gaza Strip and were locked in an intense firefight, according to witnesses.
The urban battlefields were littered with debris as frightened Gazan residents hid inside their homes and imams read Koranic verses over mosque loudspeakers.
"We hear the rockets and the explosions everywhere... we cannot leave our homes," Jabaliya resident Abu Alaa, 40, told AFP by telephone as he and his children took cover. "They're shooting at everything that moves."
The latest operation raised the death toll to more than 80 since the level of violence escalated on Wednesday.
Palestinian president Mahmud Abbas, whose forces were driven out of Gaza when the Islamist Hamas seized power in June, urged "international protection for the Palestinian people", in an appeal from the West Bank city of Ramallah.
"It is unthinkable that Israel's reaction to Palestinian rocket attacks - which we condemn - can be so terrible and frightening," Abbas said, adding that the attacks were targeting "innocent women, children and old people".
In Damascus, exiled Hamas political supremo Khaled Meshaal angrily accused Abbas of providing Israel with "a cover, voluntarily or involuntarily", to carry out its assault.
Since the peace talks were formally relaunched more than three months ago at least 284 people have been killed, the vast majority of them Gaza militants, according to an AFP count.
Robert Serry, the UN special coordinator for the Middle East peace process, called for an end to the violence, his spokesman Richard Miron told AFP.
Serry "called for an immediate cessation of rocket fire at Israeli civilians and reminded the IDF [Israeli army] that it must comply with international humanitarian law and not endanger civilians," Miron said.
Christopher Gunness, a spokesman for the UN agency for Palestinian refugees (UNRWA), said "those on both sides responsible for the killing of civilians must be held accountable".
In Ramallah, about 300 Palestinians from all the major political factions marched through the streets, carrying pictures of children killed in the Israeli strikes.
At least 16 militants were killed in Saturday's operation, most of them from the Hamas movement, medics said. One of those killed, Abdelrahman Shihab, was the son of Hamas MP Mohammed Shihab.
Gaza militants fired at least 40 rockets and mortars at southern Israel, including eight long-range rockets which crashed in and around the town of Ashkelon, 11 kilometres north of Gaza, the army said.
Six Israelis were wounded by the rockets that fell on Ashkelon, one of them seriously, it added.
Deputy Defence Minister Matan Vilnai told public radio that Israeli forces were engaged in an "enlarged operation," but denied it was the start of a major campaign aimed at partly reoccupying Gaza.
Senior Israeli political and military leaders have been mulling a major ground operation for months, as Palestinian militants have launched near-daily rocket and mortar attacks on southern Israel.
The latest deaths brought to at least 6,245 the total number of people killed in Israeli-Palestinian violence since 2000, most of them Palestinians, according to an AFP count. (AFP)
Israel kills 49 Palestinians as peace process ‘buried’