GAZA CITY (CNN) -- Fighting between Israeli troops and Palestinian gunmen in Gaza City set part of a U.N. relief agency's central storehouse for humanitarian aid ablaze, its director said Thursday.
The fire left black smoke hanging over Gaza City, and there was no way to control the fire, said John Ging, the head of operations in Gaza for the U.N. Relief and Works Agency.
"It's a very big fire, and we're not able to get it under control at the moment," he said. With gun battles going on around the facility, "the emergency services are not able to get to us."
The compound was hit by shrapnel and tank fire during clashes Thursday morning, Ging said. Three workers were hurt, and the compound's warehouse and workshop were burning out of control within an hour and a half, he said. Video Watch as fire blazes at U.N. compound »
"What we've had all night and into this morning is a relentless bombardment of this area by artillery fire, which is coming from kilometers away, and by tank fire," he said. He said staffers identified the source of the fires as white phosphorous shells, whose use is restricted under international law.
There was no immediate comment from the Israeli military on the allegation. But the U.S.-based group Human Rights Watch has accused Israel of using white phosphorous shells in Gaza during its campaign against Hamas, which has ruled Gaza since 2007.
The group said that while the use of white phosphorus to obscure military movements is "a permissible use in principle," the substance can burn civilians and start fires in the densely populated region.
The Israel Defense Forces initially denied using the ordnance. But by Monday, Israeli officials said only that any shells fired in Gaza "are in accordance with international law."
Aid workers were already warning that the new fighting between Israel and the Palestinian militant group Hamas threatened to bring about a humanitarian disaster. Following the last two days of bombardment, the private relief agency CARE announced it was canceling its distribution of food and medical aid to the territory during Thursday's fighting as well. Read an aid worker's diary
"Desperately needed supplies are ready to be distributed today, but we cannot reach the people in need because of the bombing," Martha Myers, the charity's director in the Palestinian territories, said in a written statement.
And the Foreign Press Association said international news agency offices in Gaza City was hit by Israeli fire Thursday and demanded Israel stop shooting at the building that houses them.
"We note that these buildings are well known landmarks in Gaza and that the IDF has been clearly notified of their location on several occasions," the agency said.
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UNRWA spokesman Christopher Gunness said the agency had urged Israel to stop fighting nearby, but had no response. U.N. Secretary-General Ban Ki-moon, who is in the region for talks aimed at ending the now 20-day war, was meeting Israeli Defense Minister Ehud Barak as the fire burned.
Gunness urged both Israel and Hamas, which has been firing rockets into southern Israel, to heed the "conscience of the world" and comply with a U.N. resolution calling for a cease-fire.
But he added: "I'm standing looking over the town of Beit Hanoun, and with every dull thud and every plume of smoke that comes out of there, it's sad to say that the parties on the ground are not listening."
Israeli aircraft struck 70 targets in Gaza overnight, the Israel Defense Forces reported Thursday, while fighting on the ground left 11 Israeli troops wounded. The military said about 35 armed Palestinian fighters were wounded or killed in those clashes, mostly by airstrikes.
The Israeli military has been halting its bombardment for daily three-hour stretches to allow trucks loaded with food, fuel and medical supplies to enter the territory. It said it planned to let 170 trucks through the border on Thursday, and announced the appointment of an army officer, Brig. Gen. Shimi Daniel, to coordinate humanitarian efforts. Video Watch as civilians suffer most »
Israel launched its campaign against Gaza on December 27 in an effort to halt the firing of rockets at its southern cities. That fire persisted Thursday, with at least 10 rockets or mortar shells striking Israeli territory, the IDF reported.
More than 1,000 Palestinians have been killed and nearly 5,000 wounded since the conflict began, Palestinian officials said Wednesday. Israel said 10 of its soldiers and three civilians have been killed and more than 100 soldiers have been wounded.
Hamas refuses to recognize Israel's right to exist and has been designated a terrorist organization by the Israeli government, the United States and the European Union. A top official of the movement, which won Palestinian elections in 2006, said Wednesday it would accept a cease-fire only if the Jewish state withdraws from Gaza and lifts its economic blockade of the territory.
The issue has split the Arab nations into two camps: Those, like Egypt, who want an end to Hamas' political influence, and others, like Qatar, who are more sympathetic to the movement.