JERUSALEM — Israeli warplanes bombarded a U.N. post in southern Lebanon on Tuesday, killing four observers in a strike that Secretary-General Kofi Annan termed "apparently deliberate."
The bombing capped a violent day that included the death of a 15-year-old Israeli girl from a Hezbollah rocket in a northern Galilee town, and renewed Israeli airstrikes in and around Beirut.
United Nations officials said their observation post near the village of Khiam took a direct hit late Tuesday in an Israeli airstrike. Four members of the mission were killed. Their names and nationalities were not immediately released.
Annan flew to Rome to meet with U.S. Secretary of State Condoleezza Rice and diplomats from European and Middle Eastern nations about the Lebanon crisis. He said he was "shocked and deeply distressed" by what he said was the "apparently deliberate" targeting of the post by the Israeli army.
Annan said he had received personal assurances from Israeli Prime Minister Ehud Olmert that U.N. positions would be spared, and the U.N. force commander for south Lebanon, Gen. Alain Pellegrini, had been in repeated contact with Israeli officers to ensure the post's protection.
American officials labeled the attack "a terrible tragedy" and said they were told by the Israelis that it was an accident.
There was no immediate statement from the Israeli military, but Israel's ambassador to the United States said the incident was under investigation, and reacted sharply to Annan's allegation that the strike was deliberate.
"I think this kind of rhetoric is deplorable, it's outrageous, and I hope he will apologize for that," Ambassador Daniel Ayalon said on CNN's "The Situation Room."
He accused Hezbollah militants of positioning rocket launchers beside U.N. sites, a practice that has been reported by U.N. officials in recent days.
Hezbollah commander Sheik Hassan Nasrallah expressed new defiance late Tuesday. In a televised address, he said his organization would not submit to "humiliating" conditions imposed by the international community for a cease-fire, and threatened attacks even deeper into Israel.
Referring to a "new period" in the 2-week-old conflict, he said Hezbollah would strike beyond the port of Haifa, Israel's third-largest city, where scores of rockets have been falling by the dozens.
"We will choose the time when we will move beyond -- beyond Haifa," Nasrallah said.
The U.N. deaths came as Western nations were set to meet today in Rome to discuss a possible cease-fire, response to the growing humanitarian crisis in Lebanon, and a possible international peacekeeping force.
The Bush administration did not budge from its stance that Israel should be allowed to deal a more decisive blow to Hezbollah before any cease-fire. Rice, in Jerusalem, stood by Olmert as he pledged to "carry on the fight" against the Shiite Muslim militant group.
Before she left for Rome, Rice visited the West Bank city of Ramallah, and again turned aside calls from the Lebanese for an immediate cease-fire. She said an "enduring" peace was more important and possible only with the disarming of Hezbollah.
"It is time for a new Middle East," she said, with Olmert nodding approvingly at her side. "And to those who do not want a new Middle East, we say we will prevail, they will not."
"Israel is determined to carry on the fight against Hezbollah," Olmert said. "We will stop them. We will not hesitate to take the most severe measures against those who are aiming thousands of missiles and missiles against innocent civilians for one purpose -- to kill them."
Henry A. Crumpton, the State Department's coordinator for counterterrorism efforts, said Tuesday that he believed the Israeli response was "in some ways just beginning," noting that Israel's military has made only limited progress in degrading Hezbollah's capabilities.
Ground fighting continued Tuesday, with Israeli armor and infantry battling guerrillas for control of the Lebanese town of Bint Jbeil. By the end of the day, field commanders said they had seized the town, the largest in the border region and considered by Israel to be a Hezbollah headquarters.
The Israeli military said 20 to 30 Hezbollah gunmen were killed in the fighting around Bint Jbeil on Tuesday. An Israeli soldier was wounded in a fresh gunfight around Maroun el Ras, a hilltop village about 1 1/2 miles north of the border, near the Israeli community of Avivim.
Returning troops described a tenacious adversary.
"There are places I've been that were pretty smooth. This is not one of them," said Assaf Oppenheimer, a 20-year-old medic, who has marched into Lebanon a couple of times now. "They're putting up a hell of a fight.... They might be terrorists, but they're an army."