As the invasion continued on Wednesday, an Israeli helicopter gunship fired two rockets on a metal workshop in the Jabalya area, lightly wounding two people, witnesses said.
Two fighters of the largest resistance group, Hamas, were shot dead by Israeli troops as they attempted to infiltrate the Kfar Darom Jewish settlement in the southern Gaza Strip. A third fighter died when an explosive charge he was carrying went off prematurely.
A Thai migrant labourer employed on the settlement died during exchanges of fire between the Palestinians and Israeli troops.
Earlier, medics said three Palestinians were killed in Israeli tank strikes in the northern Gaza Strip overnight. Twenty Palestinians were reported wounded, two of them young women who were said to be in serious condition.
The deaths brought to 88 the number of Palestinians killed since the army launched its offensive against the northern Gaza Strip on 28 September.
But Hamas remained defiant on Wednesday, warning it would "continue and increase rocket firing" on Israel" and would "not stop launching rockets even if Israel leaves the northern Gaza Strip".
"The resistance will not stop and, whether it wants to or not, the enemy will have to leave northern Gaza under rocket fire," masked fighters from Hamas' military wing - the Izz al-Din al-Qassam Brigades - told reporters in the town of Bait Lahya.
Scores of Palestinians have been
killed in the last two weeks
The crude and highly inaccurate Qassam missiles have a range of 10km and can carry a 5kg payload. Hamas said it had developed a marginally longer-range version.
Israeli officials were unrepentant about their onslaught, despite the mounting international criticism, which saw 11 countries support the critical draft resolution on Tuesday night and three abstain, with Washington alone in expressing opposition.
Elsewhere in the Palestinian territories a Palestinian teenager was killed by Israeli army fire in the northern West Bank town of Tulkarim.
Adding to the continuing pressure on the collapsing peace process, Sharon's top aide, Dov Weisglass, said that the goal of the premier's Gaza pullout plan was to undermine the US-backed peace road map.
"The significance of the disengagement plan is the freezing of the peace process," Weisglass told the Israeli daily Haaretz.
"And when you freeze that process, you prevent the establishment of a Palestinian state, and you prevent a discussion on the (Palestinian) refugees, the (final) borders and Jerusalem," he said, referring to steps promised in the bluepint.
Sharon's office later put out a statement, saying the prime minister "supports the roadmap, the only plan liable to help progress towards a viable political agreement".
Israel is wavering on whether
Palestine will be a sovereign state
In justifying its veto at the Security Council, Washington pointed to the draft resolution's failure to refer to Palestinian rocket fire on southern Israel.
Sharon has made reference to rocket attacks as the pretext for the invasion, but he has also been in a political quagmire with his own hardliners in government who have been keen to launch a massive attack against the Palestinians.
Many observers believe Sharon is keen to break the back of Palestinian resistance groups before an evacuation of settlers and troops from the Gaza Strp.
The proposed resolution had called, among other things, for "the immediate cessation of all military operations in the area of northern Gaza and the withdrawal of the Israeli occupying forces from that area."
Hamas said the veto served to show that the US administration was "a partner in the Israeli aggression".
It also claimed on its website that its military wing killed at least three members of a column of 50 Israeli troops in Jabaliya on 4 October.
There was no comment on the claims from the Israeli army but the website said photographic evidence would soon be provided.