GAZA CITY, Gaza Strip — The Israeli military punched deeper into Gaza City on Thursday with a series of strikes that hit the United Nations' headquarters, a major hospital and the offices of international news media groups, even as Israeli leaders weighed an Egyptian initiative for ending the 20-day-old conflict.
For the second time in the offensive, Israel said it had killed a top Hamas political leader in the Gaza Strip. Late Thursday, an airstrike hit Said Siam, who served as interior minister when Hamas won elections to take control of the Palestinian Authority in 2006. On Jan. 1, Israeli forces killed Nizar Rayan, a top military strategist.
Israeli forces hit a Red Crescent hospital Thursday, and more than 100 staff members and patients were trapped as a blaze engulfed the administration building. However, the most spectacular strike came when Israeli forces fired on the U.N. compound in Gaza City, setting off a blaze that sent a pillar of charcoal-black smoke hundreds of feet into the sky.
The attacks coincided with visits to Jerusalem by U.N. Secretary-General Ban Ki-Moon and Jakob Kellenberger, the president of the International Committee of the Red Cross. Both protested vigorously.
"It is unacceptable that wounded people receiving treatment in hospitals are put at risk," Kellenberger said.
Ban said that Israeli Defense Minister Ehud Barak had apologized for the attack on the U.N. compound.
"The defense minister said to me it was a grave mistake and he took it very seriously," Ban said before meeting with Israeli Foreign Minister Tzipi Livni to discuss U.N. efforts to end the fighting immediately.
Another strike hit several high-rise buildings, including one that houses the Reuters news offices.
Reuters had given the Israeli military the location of its office before the fighting broke out last month. On Thursday, as the Israeli forces moved in, Reuters staff members said, they called the Israeli military to remind it where they were.
Two minutes after the call, a shell hit the office, the Reuters staff said.
The Associated Press reported that gunfire struck its office in a separate building.
Thursday's attacks came as Israeli negotiator Amos Gilad met with Egyptian diplomats who are trying to broker an end to the fighting, which has claimed nearly 1,100 Palestinian lives.
While Hamas leaders say they back the Egyptian plan in principle, they haven't yet agreed to the details.
In addition to the Egyptian cease-fire proposal, Israel is seeking a side agreement with the United States for an expanded international effort to stop arms shipments from reaching Hamas, diplomats said.
In a sign that the U.S.-Israeli agreement is close, Israel announced that Livni would travel to Washington. The side agreement would make it easier for Israel to accept a cease-fire, and it represents the country's last chance to secure support from the outgoing Bush administration.
The diplomats said that under the draft agreement, the United States and Israel would share intelligence and cooperate to prevent weapons from reaching Egypt's side of the border with Gaza. Most of the weapons are thought to come overland across Egypt's Sinai peninsula, while some are smuggled by ship in the Mediterranean.
The diplomats spoke only on the condition of anonymity because the negotiations are ongoing.
Relations between the U.N. and Israel have been strained by Israeli attacks in Gaza that have killed U.N. staff members, students and refugees seeking refuge in temporary shelters, and they came under new stress Thursday.
Israeli officials issued contradictory versions of why their forces had fired on the U.N. An anonymous Israeli military official first told the AP that Gaza militants had fired antitank weapons and machine guns from within the U.N. compound.
Then Israeli officials came forward to say that preliminary results showed that the militants had run into the compound for safety after firing from outside it.
Chris Gunness, a spokesman for the U.N. refugee agency, dismissed the Israelis' claims as baseless and challenged them to produce evidence to back up their story.
In the worst such incident, 43 Palestinians were killed last week when an Israeli strike hit a U.N. school where hundreds had sought safety.
Then, as now, Israeli officials initially claimed that Hamas militants had fired from the school. After the U.N. denied that charge, Israel later said that its soldiers had fired at Hamas militants who'd been firing mortars near the school.
On Thursday, Gunness said that Israel's shifting stories raised questions about its veracity.
"With every flip-flop, Israel's credibility is severely undermined," he said.
About 1,100 people have died and more than 4,500 reportedly have been wounded as Israeli forces have taken aim at densely populated civilian areas that military officials say Hamas fighters use as cover. On the Israeli side, 13 people have died, 10 of them soldiers.
As Israeli soldiers clamped down Thursday on Gaza City, thousands of residents fled their homes looking for safety, many in their nightclothes.
Responding to the assaults on buildings housing media, the Foreign Press Association in Israel denounced the "unconscionable breaches" and urged members not to distribute or broadcast photos or video that the Israeli military gave them until there's a formal apology.
Since early November, Israel has imposed a near-blanket ban on international reporters entering Gaza.
Israel's high court has directed Israel to allow reporters into Gaza during the fighting, but the Israel Defense Forces have refused to do anything more than take selected journalists on short embeds with troops.
"The FPA rejects and condemns the IDF policy of controlling the news coverage of the events in Gaza," the association said Thursday in a statement. "By preventing the entry of foreign journalists into Gaza and bombing buildings housing offices of international media — contrary to IDF assurances that these media buildings would be safe — the IDF is severely violating basic principles of respect for press freedom."
Israeli officials have said that their forces don't intentionally target civilians and they reject allegations that they've violated international laws in the conflict.
(Hamda is a McClatchy special correspondent. Nissenbaum reported from Jerusalem. Warren P. Strobel contributed to this article from Washington.)
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