UNITED NATIONS — As condemnation of Israel resounded around the world and Arabs called for the deployment of a U.N. force, a top Hamas official threatened violent retaliation yesterday for the deaths of 19 Arab civilians in Gaza.

The threat was taken seriously in Israel, where internal security forces were put on high alert to prevent suicide bombings and other terrorist activities.

While Jerusalem was quick to launch an investigation into yesterday’s incident in the northern Gaza town of Beit Hanoun, the Israel Defense Force was roundly criticized for its ongoing military operations against Palestinian Arab rocket attacks from Gaza.

A draft resolution that Qatar circulated to the 15-member U.N. Security Council on behalf of the Arab group at the United Nations demands that Israel cease “its aggression against the Palestinian population” immediately and calls for the establishment of a “U.N. observer force to supervise the cease-fire.” The draft also proposes that a U.N.committee be established to “investigate the massacre that took place in Beit Hanoun.”

The Israeli government apologized for yesterday’s IDF artillery attack and offered humanitarian assistance to the wounded. Defense Minister Amir Peretz set up an investigation committee to determine what caused the shelling at Beit Hanoun, which killed 19.

IDF officials said the army’s policy against firing at civilians is clear. The tanks were aiming for a nearby Kassam rocket-launching site that had targeted the Israeli city of Ashkelon, officials said.

“We deeply regret the injuries and loss of life in Gaza today,” a spokesman for the National Security Council, Gordon Johndroe, said. “We have seen the Israeli government’s apology and hope their investigation will be completed quickly.”

The exiled Hamas leader, Khaled Mashaal, promised retaliation. “Our condemnation will not be in words but in deeds,” he said from Damascus, Syria. “The resistance will respond.”

Hamas sees America as responsible for “this crime” along with the “Zionist entity,” he added.

At Turtle Bay, Arab diplomats tried yesterday to build on the model of the enhanced force the United Nations sent to Lebanon this summer, to revive their long-standing idea of establishing an international presence in Gaza and the West Bank. Over the years, Israel has steadfastly resisted such initiatives, and America has opposed them in votes at the Security Council.

“It is not a peacekeeping force” like the one in Lebanon, the Egyptian ambassador to the United Nations, Maged Abdelaziz, told The New York Sun. The proposed U.N. force would “observe and report about who violates its commitments” along Gaza’s border with Israel, he said. If Egypt is asked to participate, he added, “We would consider that.” Egypt controlled Gaza between 1948 and 1967, and it remains active in Palestinian Arab politics there.

Italy, which contributed the largest number of troops to the mostly European U.N. Interim Force in Lebanon, also has suggested that a U.N. force be sent to Gaza. Italy is expected to join the Security Council in January as a non-permanent member.

U.N. diplomats and Turtle Bay officials expressed skepticism about such a force, however. “Any blue-helmet deployment would require the authorization of the Security Council and the consent of both parties,” a U.N. spokesman, Stephane Dujarric, told the Sun.

“In general, we have questions about a role for the Security Council in addressing this conflict,” an American diplomat who spoke on condition of anonymity said. The diplomat dismissed the idea of a U.N. mission. “We don’t see a role for such a force,” he said.

A European diplomat said that after a public session at the council today, the Arab group could push for a quick vote on its proposal, perhaps as early as tomorrow, with the expectation that America would veto it. The group will then try to pass the resolution at the U.N. General Assembly, which cannot establish a U.N. force but could demand an international investigation headed by the secretary-general.

The IDF commander of the southern district, Major General Yoav Galant, said the artillery round that hit the Beit Hanoun building yesterday was most likely the result of a calibration error. The target was located 500 yards away, he told Israeli reporters. IDF troops have orders to avoid targeting civilians, he added.

But Secretary-General Annan said in a statement that he was “shocked” and added that he had warned Prime Minister Olmert in a phone conversation Friday that the army operations would “inevitably cause civilian casualties.”

The British foreign secretary, Margaret Beckett, also condemned the Israeli strike. “It is hard to see what this action was meant to achieve and how it can be justified,” she said in a statement.