BEIRUT (Reuters) - Israeli bombing of a Beirut neighborhood where Hizbollah had its headquarters has breached humanitarian law, a senior U.N. official said on Sunday.

"It is horrific. I did not know it was block after block of houses," Jan Egeland, the U.N. emergency relief coordinator, told reporters as he toured the shattered Haret Hreik district. "It makes it a violation of humanitarian law."

"It's bigger, it's more extensive than I even could imagine," he said, surveying a pile of rubble.

Israeli warplanes have pounded the area nearly every night since its war with Hizbollah began on July 12.

It was last hit early on Sunday, said the few residents not to have fled the usually packed area.

Egeland said between half a million and a million people were in need of international assistance in Lebanon, but delivering aid required safe access. "So far Israel is not giving us access," he said.

Egeland plans to travel to Israel on Tuesday to negotiate safe corridors by land, sea and air. He has estimated that $100 million is urgently needed to help avert a humanitarian crisis.

"There is definitely a humanitarian crisis unfolding in Lebanon," he said. Israel's bombardment of its northern neighbor has killed 359 people, mostly civilians.

Egeland leafed through the pages of books scattered among the rubble in the Shi'ite Muslim quarter, where air raids have flattened a Hizbollah compound of buildings and destroyed homes.

PEOPLE UNDER SIEGE

Two veiled women carrying possessions in plastic bags made their way past the U.N. official.

"We are setting up a major relief operation but the violence has to stop," Egeland said, calling for a halt to the war.

"The rockets going into Israel have to stop," he said. "The enormous bombardment that we have seen here with one block after another being leveled has to stop."

The Israeli government said the military was trying to be as precise as possible in its operations in Lebanon.

"The Lebanese people are not our enemy. We cannot sit idly by while Hizbollah terrorists launch rockets at our towns and cities," Israeli Foreign Ministry spokesman Mark Regev said.

Hizbollah attacks and rockets have killed 37 Israelis. The war was sparked by the group's abduction of two Israeli soldiers in a raid into Israel.

Egeland said the United Nations was planning to deliver aid using a fleet of trucks and by ship into Beirut and the southern city of Tire.

"We're particularly worried for this area of Beirut and for the southern part of the country," he said.

"There are wounded who do not get sufficient treatment. There are people who do not have safe drinking water. There are, first and foremost, tens of thousands of people who are now being besieged, or in areas (of) cross fire," he said.

"It is costing too many lives and it will not lead to a solution in the south. There is no military solution to these things, it is only a political solution."

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