JABALIYA, Gaza Strip (AFP) - Seven Palestinians were killed during a massive Israeli incursion into the northern Gaza Strip, as Washington urged Israel to use only proportionate force and bear in mind the consequences of their actions, while refusing to condemn the operation.
The deaths came after Israeli Prime Minister Ariel Sharon ordered the army to step up a raid started Tuesday aimed at stopping militant rocket attacks on southern Israel.
Forty-five Palestinians have been killed over the past three days along with two soldiers and a woman settler in one of the bloodiest battles since the Palestinian uprising started four years ago.
The latest campaign, codenamed "Days of Penitence", intensified after two Israeli toddlers were killed in Sderot, less than a kilometre (a mere half mile) across the Gaza border.
Thirty-five tanks were seen entering the town of Beit Hanun at dawn Friday, while another 30 were seen pushing into Beit Lahiya and 30 more spotted moving into the eastern sector of the Jabaliya refugee camp, residents said.
The White House cautioned the staunchest US ally in the Middle East to "keep in mind the impact" of such actions on the peace process, while declining to condemn Israeli action.
"There continues to be ongoing violence. We've always said Israel has the right to defend itself, but it's also important to keep in mind the impact of those decisions," spokesman Scott McClellan told reporters.
The US State Department called on Israel to use only "proportional force" in its military operations in Gaza and urged the Jewish state to avoid civilian casualties which it said complicated Middle East peace efforts.
The Arab League roundly condemned the incursion and criticized the international sponsors of the Middle East peace process for not speaking out.
One Palestinian was killed and seven wounded by an Israeli rocket fired on the Jabaliya refugee camp, medics said, while the Israeli military said that another Palestinian had been killed after militants tried to storm the Erez border crossing between the northern Gaza Strip and Israel.
The botched attack was jointly claimed by the Islamist Hamas movement and the Al-Aqsa Martyrs' Brigades, a radical group affiliated to Palestinian leader Yasser Arafat's Fatah movement.
The other five of Friday's Palestinian victims died in two air raids on Jabaliya, sources on both sides said.
Two were Hamas militants. An army spokeswoman said they were about to fire a Qassam rocket. Palestinian witnesses said an unmanned plane had fired on the Hamas men.
Medics said at least 14 people had been wounded in the two air strikes and that a third one, also on Jabaliya, had wounded another person.
"The activity in Gaza has one clear overriding aim -- to prevent the firing of Qassam rockets at Sderot and the firing of mortar shells at Jewish settlements in Gaza," Defence Minister Shaul Mofaz said while meeting troops about to be deployed in the northern Gaza Strip Friday afternoon.
Troops were preparing to take control of a six-kilometer (four-mile) deep buffer zone in the northern Gaza Strip to keep militants out of rocket range of southern Israel, a close aide to Sharon told AFP.
The aide said the army could "be more aggressive" if militant rocket attacks continued.
Two rockets did hit Sderot Friday, but without causing any casualties, the army said.
Fatah movement and the Al-Aqsa Martyrs' Brigade called for a "Day of Rage" to be organized Saturday in response to the Israeli action.
A joint statement called on "all militant Palestinians to take part in demonstrations of solidarity with our families in the northern Gaza Strip who are facing the Zionist machine of oppression that is committing a massacre."
The UN Relief and Works Agency for Palestinian refugees (UNWRA) accused the Israeli army of taking over schools while pupils were still in class, and using them as firing positions.
"They have now taken positions in these three schools and are using them as a military camp for their ongoing campaign, using them also as firing positions," UNRWA spokesman Matthias Burchard said in Geneva.
"UNRWA strongly protests the totally unacceptable misuse of clearly marked UN installations and calls on the Israeli military to respect the neutrality of these places."
The latest deaths brought the overall toll since the start of the Palestinian uprising to 4,400, including 3,376 Palestinians and 953 Israelis, according to an AFP count.