GAZA CITY (AFP) – Missiles demolished a school in Gaza on Saturday as the Israeli assault on Hamas entered its second week, with truce bids stalled and Islamists vowing a “black destiny” if ground troops move in.

Concern rose over the humanitarian situation in one of the world’s most densely populated and impoverished places where the vast majority of the population depends on foreign aid.

With international efforts to reach a ceasefire stalled, anger in the Muslim world has spiralled and protests against one of Israel’s deadliest ever assaults on Gaza have mushroomed around the globe.

The United States gave its close ally free rein to press ahead with a threatened ground offensive into Gaza , saying the key to a truce was Israel’s demand that Hamas permanently stop firing rockets.

“I think any steps they are taking, whether it’s from the air or on the ground or anything of that nature, are part and parcel of the same operation,” said White House spokesman Gordon Johndroe.

“Those will be decisions made by the Israelis.”

Hamas’s Syria-based chief Khaled Meshaal told Israel that “if you commit the stupidity of launching a ground offensive then a black destiny awaits you.

“You will soon find out that Gaza is the wrath of God,” he said in pre-taped remarks broadcast on Al-Jazeera television late on Friday.

President George W. Bush, meanwhile, urged all able parties to press Hamas to stop firing at Israel to facilitate a lasting ceasefire.

“The United States is leading diplomatic efforts to achieve a meaningful ceasefire that is fully respected,” Bush said in his weekly Saturday radio address, the text of which was released late on Friday.

“I urge all parties to pressure Hamas to turn away from terror, and to support legitimate Palestinian leaders working for peace.”

Bush blamed Hamas for the latest violence and rejected a unilateral ceasefire that would allow the Islamists to continue targeting Israel with rocket and mortar fire.

On the ground, Israeli tanks and troops stood ready along the 60-kilometre (37-mile) border with Gaza, waiting for the green light from the government to advance.

Since unleashing “Operation Cast Lead” in retaliation for consistent rocket fire from Gaza on December 27, at least 436 Palestinians have been killed and 2,290 wounded in some 750 strikes carried out by air and sea, Israeli officials said.

At least 75 of those killed have been children, according to emergency services inside Gaza.

The strikes have demolished Hamas government buildings, the homes of senior Islamist officials, mosques alleged to have stored weapons, roads and tunnels used to smuggle arms and supplies into the territory that Israel has virtually kept sealed since Hamas seized power there in June 2007.

But the offensive has failed to halt rocket fire from the territory, with militants firing some 500 rocke ts and mortar rounds at Israel over the past week, killing four people and wounding several dozen others.

In the latest 25 raids carried out overnight and early on Saturday, missiles demolished a school in northern Gaza, killing a guard in a strike the army said targeted “a college used as a base for firing a large number of rockets.”

Missiles also slammed into Gaza City port and a strike killed Mohammad al-Jammal, 40, who sources in Gaza said was a local commander of Hamas’s armed wing.

The Israeli military said Jammal was responsible “for the entire rocket launching enterprise in all of Gaza City.”

Militants responded overnight with seven rockets and mortar rounds without causing any casualties, the army said.

The Israeli bombardment has demolished dozens of houses as it destroyed Hamas infrastructure amid heightened concern over the humanitarian situation in besieged Gaza, where most of the 1.5 million residents depend on foreign aid.

“By any definition this is a humanitarian crisis and more,” said Maxwell Gaylard, the UN humanitarian coordinator for the Palestinian territories.

Meanwhile French President Nicolas Sarkozy was due to arrive in Israel on Monday for ceasefire talks, a day after the arrival of foreign ministers from current European Union president the Czech Republic, Sweden and France.