RAFAH, Gaza Strip — Israeli helicopters pounded this refugee camp on the border with Egypt with missiles and machine gun fire Tuesday, killing at least 19 Palestinians as troops searched houses in an offensive that drew worldwide condemnation.
The United States said it was seeking clarifications from Israel about the operation, the biggest in Gaza in years. Officials said it would last at least a week.
The army said most of those killed were gunmen. Palestinians said at least nine civilians were among the dead, including a brother and sister, ages 13 and 16, who were killed by shots from a nearby army position while taking down laundry from a rooftop.
The death toll was expected to rise, with doctors saying they had reports of two bodies that ambulances were unable to collect.
In the West Bank, two Palestinians were killed by army fire — one in the city of Nablus and one near Jenin.
Trapped Rafah residents huddled in the innermost rooms of their homes as bullets rained outside. Others tried to flee to safer ground; since the weekend, thousands of Rafah residents have left their homes. At least 42 Palestinians were wounded, including 12 who were in serious condition.
Israel says it is targeting the Rafah refugee camp to destroy arms-smuggling tunnels and hunt Palestinian militants. Security officials said earlier this week the army also plans to widen an Israeli patrol road between the camp and Egypt, which would entail demolishing rows of nearby houses.
However, army officials said Tuesday there would be no systematic demolitions.
Last week, Israel destroyed about 100 houses near the patrol road, making more than 1,000 Palestinians homeless and drawing condemnation from around the world.
A report released Tuesday by Amnesty International said Israel is guilty of war crimes for its destruction of thousands of Palestinian homes in the West Bank and the Gaza Strip.
The human rights group called on Israel to halt the practices immediately, saying the destruction was disproportionate to Israel's security needs and represented "grave breaches of the Fourth Geneva Convention and are war crimes."
Responding to the report, the Israeli Foreign Ministry said Palestinian militants use houses in civilian neighborhoods to attack Israeli forces and as cover for weapons-smuggling tunnels.
The first phase of Israel's offensive, "Operation Rainbow," struck the Tel Sultan neighborhood on the outskirts of the Rafah camp Tuesday, about two miles from the patrol road.
Bulldozers began tearing up a road to separate the neighborhood from the rest of the camp, home to about 90,000 Palestinians, witnesses said. Soldiers backed by about 70 armored vehicles went house-to-house in the neighborhood.
Ahmed Mughayer, 13, and his 16-year-old sister Asma were on the roof of their three-story apartment building when they were hit by army fire, said their older brother, Ali. The shots were fired from an Israeli army position on the sixth floor of the neighboring building, Ali Mughayer said.
He said that when he heard the shots, he raced upstairs and saw his siblings lying on the ground. Mughayer said that as he tried to pull the bodies, he himself came under fire. "I was crawling on the roof because of the fire, and with great difficulty, I finally got them out," he said.
The army had no immediate comment on the deaths.
In all, 19 Palestinians were killed by Israeli fire — 10 in two separate missile strikes, and nine by machine gun fire, said Dr. Moawiya Hassanain, a senior Palestinian Health Ministry official. A 20th man was killed while handling explosives.
The raid began before dawn Tuesday with two missile strikes the army said were aimed at gunmen. A missile hit a group of gunmen outside a mosque in Tel Sultan, killing three. Two more missiles were fired, killing three more people who rushed to help. The mosque caught fire. In another airstrike, four Palestinian civilians were killed, according to hospital officials.
Troops also demolished four houses in Tel Sultan, witnesses said. In all, more than 11,000 Palestinians in Rafah have been made homeless by Israeli demolitions since the outbreak of Israeli-Palestinian fighting in 2000.
With the dead streaming to Abu Yousef Al Najar Hospital in Rafah, the morgue filled up and bodies wrapped in white cloth were laid on the ground in a storefront next to a falafel stand.
Palestinian ambulance drivers reported coming under fire and many were unable to evacuate wounded.
Dr. Wael Burdeini said troops besieged a clinic in Tel Sultan, with a tank and an army bulldozer parked outside, and there was heavy shooting in the area. "Two pregnant women called for urgent medical care, and one of them delivered at home," Burdeini said.
The Israeli military denied besieging the clinic, saying gunmen were firing from nearby at Israeli troops and drawing return fire. The army also said it was permitting some ambulances to drive to a larger hospital in neighboring Khan Younis.
Israeli army chief Lt. Gen. Moshe Yaalon said Israel has no choice but to act because Palestinian militants have succeeded in smuggling rocket-propelled grenade launchers into Rafah, with the help of Iran and the Iranian-funded Hezbollah guerrilla group in Lebanon.
Paul Patin, a spokesman for the U.S. Embassy in Tel Aviv, said the United States has asked Israel for clarifications regarding the Rafah operations.
Arab nations asked for a special session of the U.N. Security Council about the situation in Gaza, and Secretary-General Kofi Annan denounced the Israeli operation. Amr Moussa, the secretary-general of the Arab League, condemned the destruction and described Israeli actions in Rafah and Gaza as "war crimes."
Jordan called on Israel to stop its assault and return to negotiations with the Palestinians. In a statement carried by the official Petra news agency, it said home demolitions and the killings of unarmed Palestinians "represent flagrant and direct aggression against thousands of citizens and threaten directly the stability of the Palestinian territories in particular, and the region in general."
European Union foreign policy representative Javier Solana said the destruction of homes "goes very much against the letter and the spirit of the road map" plan for Israeli-Palestinian peace. An EU enovy, Marc Otte, was in Israel for talks with Israeli leaders, his aides said.
Israeli Prime Minister Ariel Sharon has proposed a unilateral pullout of soldiers and settlers from Gaza, but his party turned down the plan in a nonbinding referendum. Officials said Monday that he would make minor revisions in his plan over the next two weeks and present it to his Cabinet.