Israeli helicopters attacked a Hamas (search) training camp early Tuesday, killing at least 14 militants and wounding 30 others in one of the deadliest airstrikes since fighting broke out four years ago.

The attack came a week after Hamas suicide bombers blew up two buses in the Israeli city of Beer Sheba, killing 16 people.

In an unusually strong statement, Palestinian Prime Minister Ahmed Qureia (search) warned that that airstrike would bring Hamas retaliation, which he said would be "justified."

"No crime goes unpunished," Qureia said of the Israeli attack at a meeting of the Palestinian Cabinet. "For sure there will be retaliation, and the retaliation will be justified if it happens."

Hamas, which has carried out dozens of deadly attacks inside Israel, vowed revenge. Hours after the attack, Palestinian militants fired mortars and homemade rockets at Jewish settlements in the Gaza Strip (search) and the border town of Sderot (search). One Israeli in Sderot was slightly wounded in a rocket attack, rescue officials said.

The army said it struck a field where "senior Hamas terrorists" had trained militants to fire mortars and rockets. In the past month, Hamas assembled a large bomb and a suicide bomber's explosives belt at the training camp, the army added.

"No one is immune when he carries out terrorist attacks against innocent Israeli civilians," said Israeli Foreign Minister Silvan Shalom.

In Gaza City (search), children stayed home from school Tuesday and shops remained closed in a sign of mourning. Black smoke billowed over the city as students burned tires at spontaneous demonstrations.

Some 30,000 people, including dozens of gunmen from Hamas and other militant groups, joined a funeral procession Tuesday in Gaza City. As militants fired machine guns into the air, the crowd screamed for revenge.

"Our response to this crime is coming, God willing. and our twin attack in Beer Sheba is only one part of many strikes to come," a Hamas militant screamed over loudspeakers mounted on a car.

In the West Bank, Qureia said the airstrike undermined peace efforts, noting that it came a day after Egyptian officials visited the West Bank. Israel is planning to withdraw from Gaza next year, and Egypt has stepped in as a mediator to ensure security in the area after the pullout.

Israeli Prime Minister Ariel Sharon (search) refuses to negotiate directly with the Palestinians, saying they are not a serious peace partner.

Since the current round of fighting with the Palestinians broke out in September 2000, Israel has frequently targeted militants through airstrikes and other military operations.

But the strikes are usually aimed at very specific targets — usually senior militants or activists on their way to an attack. Last spring, Israeli killed Hamas' spiritual leader and his successor in separate strikes three weeks apart.

This policy, which Israel calls "targeted killings," has enraged the Palestinians and drawn international criticism, especially because of frequent civilian casualties.

Tuesday's attack was the first time the army has targeted such a large gathering of militants.

In the deadliest airstrike, an Israeli F-16 warplane killed a Hamas leader, Salah Shehadeh, along with 14 other people, including nine children, in July 2002.

In October 2003, 14 Palestinians were killed in an Israeli missile strike in a Gaza refugee camp. Palestinians said only two of the dead were militants; Israel put the figure much higher.

In Tuesday's attack, the dead were all identified as Hamas militants. At least five helicopter missiles pounded the camp in the Shajaiyeh section of Gaza City, a known Hamas stronghold, just after midnight.

There was pandemonium at Gaza's Shifa Hospital as casualties arrived in ambulances and cars. Blood-spattered Palestinians carried dead and wounded into the emergency room, while others went straight to the morgue carrying plastic bags with body parts.

Hundreds of angry Palestinians, many of them members of the Hamas military wing with blood on their clothes, gathered outside and shouted for revenge.

The Hamas military wing said Israel had struck a "scout's camp where a group of fighters was training" and pledged revenge.

While Israel described the site as a terrorist camp, the airstrike also appeared to be linked to last week's suicide bombing in Beer Sheba, even though the bombers had come from the West Bank. Israel has historically carried out harsh retaliation following deadly attacks on its citizens.

In a separate incident in Gaza, Israeli troops fired at the Khan Younis refugee camp, critically injuring a 10-year-old girl who was walking home from school, Palestinian hospital officials said.

Military officials said they had exchanged fire with militants in the area, but had no information on a girl being hit.

Violence has increased in the Gaza Strip since Sharon announced plans this year to evacuate all Gaza settlements and four West Bank enclaves.

Palestinian groups are vying for control ahead of the planned pullout and have stepped up attacks to give the impression that they are driving Israel out of the territory. Israel, in the meantime, has increased its strikes so the pullout won't look like a victory for the militants.