Dozens of Israeli tanks backed by helicopter gunships pushed into the northern Gaza Strip early today, sparking intense gun battles with local militants and residents that left at least 11 people dead and dozens wounded, according to Palestinian security officials and hospital sources.

The Israeli army said the targets of the raid, which began about midnight and ended about 4:30 a.m., were two metal shops that were being used by militants to make homemade mortars and rockets.

In a statement, the army also said that today's operations were in retaliation for the killing Saturday of four Israeli soldiers, who died when a landmine blew up their tank in the northern Gaza Strip. The Islamic Resistance Movement, known as Hamas, a radical Palestinian group based in Gaza, asserted responsibility for the blast.

In the days since the four soldiers were killed, at least 21 Palestinians have died in counterstrikes by Israeli forces that have mostly targeted Hamas.

The attacks and counterattacks came as senior Israeli and Palestinian officials were meeting with international mediators in London to discuss Palestinian reform, economic assistance and reopening cease-fire negotiations to end the 29-month Palestinians uprising against Israel's occupation of the West bank and Gaza Strip.

In today's raid, about 40 Israeli tanks accompanied by bulldozers and helicopters plunged into the Gaza Strip from the north and east.

Four officers from the Palestinian Authority's Intelligence Service were apparently among the first to die. They were manning a new guard post outside the Jabaliya refugee camp near the Israeli border that was established about four weeks ago to prevent Palestinians from using the area as a staging ground for launching homemade mortars and Kassam rockets at Israeli targets, Palestinian security sources said.

The rocket attacks have been a major provocation for Israeli counterstrikes, and Palestinian security officials, who often have little influence with radical groups, have been trying to curtail them.

As the Israeli forces pushed deeper into Gaza, they met stiffer resistance. According to Hamas officials, one of their members, who they identified Abdul Karin Bakron, armed himself with a suicide bomb belt and blew himself up next to a tank.

The Israeli forces stopped in the Taffah neighborhood of northeastern Gaza City and placed explosives in a house owned by a Hamas militant that had a metal workshop in the basement, then withdrew from the area, Palestinian sources said. When they detonated the explosives, the blast caused part of the house next door to collapse, killing three people, including two brothers.

Meanwhile, a helicopter gunship reportedly opened fire on a group of Palestinians in a nearby field, killing at least one.

Israeli military officials said that about a dozen anti-tank rockets and grenades were fired at their forces during the operation, but no Israeli soldiers were injured. At least two more Palestinians were killed during the exchanges of fire, Palestinian security and hospital officials said.