GAZA CITY -- Israel killed a Hamas leader on Thursday in the biggest blow yet to the Islamist group's command structure as dozens more air strikes on Gaza took the death toll from the six-day blitz to at least 420.

With tanks and troops massed around the Palestinian enclave for a threatened ground offensive, Israeli warplanes and naval artillery staged more than 50 new attacks on Gaza and Hamas sent more rockets deep into Israeli territory.

Two Israeli fighter jets fired missiles on the home of Nizar Rayan in the Jabaliya refugee camp, killing the hardline firebrand speaker, his four wives, 10 of his children and two neighbors, witnesses and medical sources said.

Rayan's decapitated body was hurled into the street by the force of the blast which also destroyed or damaged 12 nearby houses.

He was the most senior Hamas figure to be killed by Israel since Abdel Aziz al-Rantissi in 2004.

"Operation Cast Lead" has now left at least 420 Palestinians dead and more than 2,100 wounded, according to Palestinian emergency services. Rockets fired from Gaza have killed four people and wounded dozens in Israel.

Thursday's Israeli strikes also hit the parliament and justice ministry in the main Hamas government complex, as well as rocket launching sites, tunnels for smuggling weapons or supplies into the territory and weapons storage facilities, a military spokeswoman said.

Hundreds of houses have been destroyed and the United Nations says about 25 percent of the dead are civilians. Food, fuel and medical supplies are all running short, according to aid agencies.

The strikes started by Israel on Saturday in response to rocket fire by Hamas and its militant allies have failed to halt those attacks. On Thursday alone, more than 50 rockets were fired, without causing casualties, the military said.

One rocket slammed into an apartment block in Ashdod more than 30 kilometers (20 miles) from the Gaza border, the army said, adding that a warplane attacked the squad that conducted the attack.

Two rockets fell near the desert city of Beersheva, 40 kilometers (25 miles) from the border -- the deepest yet they have reached inside Israel.

Speaking in Beersheva, Prime Minister Ehud Olmert said Israel is "not interested in conducting a long war" but insisted that "we will deal with Hamas and terror with an iron fist."

Hamas's armed wing said it fired three rockets at the Hatzerim air force base west of Beersheva. The Israeli army did not comment.

Hamas has fired more than 280 rockets since Saturday, according to Israel.

On the diplomatic front, Israeli Foreign Minister Tzipi Livni held talks in Paris with President Nicolas Sarkozy and other French leaders.

Israel on Wednesday rejected a French proposal for a 48-hour ceasefire to help humanitarian efforts.

Peace efforts were also stalled at the UN Security Council even though UN Secretary General Ban Ki-moon said the conflict had become "a dramatic crisis".

The civilian population in Gaza and stability throughout the Middle East "are trapped between the irresponsibility displayed in the indiscriminate rocket attacks by Hamas militants and the disproportionality of the continuing Israeli military operation," Ban said.

Libya presented a draft resolution drawn up by the Arab League to the UN Security Council calling for an immediate ceasefire.

But the United States and Britain said it appeared biased because it did not mention the Hamas rocket attacks.

In Cairo, Turkish Prime Minister Recep Tayyip Erdogan renewed his call for an immediate ceasefire and said Israel must lift its blockade in Gaza. Erdogan held talks with Egyptian President Hosni Mubarak as part of efforts to push for a Gaza truce.

Israel has massed tanks and thousands of troops around Gaza and Israeli Defense Minister Ehud Barak has warned of a ground assault to accompany the air raids.

In a defiant televised speech late Wednesday, Hamas government chief Ismail Haniya vowed Israel would be vanquished. "Our people will defeat those tanks," he said.

Israeli police said thousands of officers were deployed in and around east Jerusalem after Hamas called on Palestinians in the annexed Arab sector of the Holy City and in the occupied West Bank to mark a "day of wrath" on Friday.

The army will also lock down the West Bank on Friday and Saturday, a spokesman said. Movement in and out of the territory will be prohibited except for emergencies and special cases.

Hamas called on its website for "massive marches" following the weekly Muslim prayers on Friday, starting off from the Al-Aqsa mosque compound in Jerusalem and from "all the mosques in the West Bank."