Seven Palestinian children and six adults died today in Israeli bombardment of the Gaza Strip from air, land and sea, as President Sarkozy of France prepared for a unilateral diplomatic mission to the region.

Houses, mosques and tunnels were hit as the Israelis continued to fire into the densely populated Palestinian territory in the hopes of ending the rocket attacks from Gaza that have killed 20 people in southern Israel in the last eight years.

Ehud Barak, the Israeli Defence Minister, said that "Operation Cast Lead" would continue until Israel achieved "peace and tranquility" for residents of southern Israel.

“Gaza City is partially surrounded,” Mr Barak told parliament’s foreign affairs and defence committee. “We have hit Hamas hard, but we have not yet reached all the goals that we have set for ourselves and the operation continues. We are doing everything that a state must do to protect its citizens."

An army spokesman said that the Israeli air force had hit more than 30 targets in Gaza overnight, including a mosque in Jabaliya where arms were being stored, and houses and vehicles used by armed groups. “Ground forces continued their advance, aided by bombardment from naval ships," he said.

Dr Moaiya Hassanain, a Gaza health official, said that 13 civilians died in attacks across the Gaza Strip this morning. Four young brothers and sisters were killed in a missile strike on a house east of Gaza City. Three more children died in naval shelling of a Gaza City beach camp. Three adult civilians died when a missile struck near a house of mourning in the northern town of Beit Lahiya.

At least 524 Palestinians have been reported killed and nearly 2,000 wounded since December 27, when Israel began air raids on Gaza in retaliation for Hamas's failure to stop militants launching rocket attacks on southern Israel.

Rockets fired from Gaza into southern Israel have killed three Israeli civilians and one soldier. In addition, one Israeli soldier has been killed and 55 injured, according to a military spokesman.

There has been no unified international response to the violence. A stream of diplomats and world leaders are heading for the region to meet Israeli leaders as global outrage grows over the Palestinian casualties, but Europe has failed to agree a concerted line. The United States has blocked any action or censure by the United Nations Security Council, saying Israel has the right to "defend itself" - prompting a rare split with Britain, which has been pushing for an immediate ceasefire.

President Sarkozy, who unsuccessfully proposed a two-day truce before the invasion began and has led calls for humanitarian aid to be allowed in, was today due to meet Ehud Olmert, the Israeli Prime Minister, and Mahmoud Abbas, the Palestinian President, who lost control of Gaza to Hamas in June 2007.

Mr Sarkozy has been outspoken in condemning Israel's use of ground troops, but in interviews published in three Lebanese newspapers this morning he said that Hamas was also to blame for Palestinian suffering because its rocket attacks on southern Israel had prompted the offensive.

The French President's mission is a freelance one, however, given the European Union's failure to agree a co-ordinated response to the crisis. A separate EU delegation including Javier Solana, the bloc's foreign policy chief, was due to meet with Tzipi Livni, the Israeli Foreign Minister.

The Czech Republic, which took over the EU presidency last week, urged Israel to allow humanitarian relief aid into Gaza. Meanwhile, Chancellor Merkel spoke on the phone with Mr Olmert yesterday to advocate a quick ceasefire, the German government said in a statement.

Israeli forces invaded on Saturday, after a week of air strikes, and seized sparsely populated areas in northern Gaza over the weekend.

By this morning soldiers were dug in on the edges of Gaza City. Further movement into built-up areas would mean deadly urban warfare - with house-to-house fighting, sniper fire and booby traps - in crowded streets and alleyways familiar to Hamas’ 20,000 fighters.

Israeli troops took over three six-floor buildings on the outskirts of Gaza City, taking up rooftop positions after locking residents in their rooms and taking away their mobile phones, according to one resident. “The army is there, firing in all directions,” said Mohammed Salmai, a 29-year-old truck driver. “All we can do is take clothes to each other to keep ourselves warm and pray to God that if we die, someone will find our bodies under the rubble.”

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