EMMANUEL, West Ban ? Palestinians dressed as Israeli soldiers detonated a roadside bomb near a bus heading to a Jewish settlement Tuesday, and then sprayed the passengers with automatic gunfire as they tried to flee, military sources and witnesses said. Seven people were killed and more than a dozen wounded.

The gunmen fled the scene and were being pursued by army helicopters.

Many groups rushed to claim responsibility for the first deadly attack on Israeli civilians since June 20.

The ambush came hours before representatives of the so-called “Quartet” committee including the United States, Russia, European Union and United Nations were to meet in New York to discuss ways of ending more than 21 months of violence.

Medics who rushed to the entrance of the Emmanuel settlement in the northern West Bank quoted the wounded as saying that after the initial explosion, several smaller bombs went off, followed by shooting, Israel Radio said.

The witnesses said the attackers, about three in all, were dressed in Israel army uniforms and opened fire as the bus passengers tried to escape. The gunmen fled in the direction of Nablus, the radio report said.

“When I got there, an explosion and smoke went 10 meters (30 feet) high and stones flew over the road,” said Yitzhak Yazdi, a taxi driver. “I saw two terrorists who were running away from the road and they hid behind a rock. The soldiers came and I showed them where the gunmen were.”

Abraham Cohen, security officer at Emmanuel, said he arrived at the site a few minutes after the explosion.

“The shooting was still going on and shots were fired at my car. I was lucky to get out of my car before it was hit,” he said.

The military wing of Hamas, Izzadine al-Qassam, claimed responsibility for the attack in a telephone call to The Associated Press in Jerusalem. A man who identified himself as Nasser Asidah said the gunmen were safe in the Nablus area.

But there were other claims. Abu Dhabi TV said the Al Aqsa Martyrs Brigade, affiliated with Palestinian leader Yasser Arafat’s Fatah movement, had said it was responsible for the attack. And in a statement faxed to AP, the Syria-based Democratic Front for the Liberation of Palestine said it had carried out the attack.

Seven people were killed, said Shahar Ayalon, the police commander in the northern West Bank. Emergency officials said at least 14 people were wounded, three seriously. The injured included a 2-year-old, two 12-year-old girls and a pregnant woman, Israel TV said.

Israel blamed the Palestinian Authority for the attack.

“Israeli civilians continue to be the choice targets of Palestinian terrorists,” said David Baker, a spokesman for the government, calling the attack “further proof that the Palestinian Authority considers terrorism a primary mode of operation.”

President Bush also condemned it, White House spokesman Ari Fleischer said.

“This underscores the importance of focusing on peace and working with leaders in the Palestinian Authority who are dedicated to peace,” he said.

The Bush administration has said it will no longer deal with Arafat, saying he hasn’t done enough to fight terrorism.

Fleischer said that since Bush’s June speech calling for new leadership in the Palestinian Authority and a host of reforms “there have been some interesting rumblings from within the Palestinian Authority about the direction they would like to go in the future.”

Arafat outlined a series of reforms he has proposed in a letter to the Bush administration, but in an interview with AP over the weekend, he refused to step down. He admitted, however, that he hadn’t decided whether he would be a candidate in January elections.

On Tuesday, Mahmoud Abbas, a senior Palestinian official once touted as a successor to Arafat, told reporters in Abu Dhabi that he wouldn’t run in the elections.

No reaction to the attack was immediately available from the Palestinian Authority. Palestinian officials have said that with Israel in control of most of the cities and towns in the West Bank since last month, their security services are powerless to prevent attacks.

While Palestinian officials routinely condemn suicide attacks in Israel itself, they have rarely denounced attacks on settlements, arguing that Palestinians have a legitimate right to resist Israeli occupation in the West Bank and Gaza.

An ambush on a bus in the same area Dec. 12 killed 11 Israelis. In that attack as well, Palestinians placed a roadside bomb to force the bus to stop, then opened fire as passengers fled. In that ambush, rescue teams were also caught in the shooting.

The last fatal attack on Israelis occurred June 20, when a gunman killed five Israelis in the Jewish settlement of Itamar, near Nablus in the north West Bank.

The lull in attacks was widely seen in Israel as evidence that the policy of reoccupying the Palestinian Authorities’ autonomous zones was the best method for preventing further attacks on Israelis.

Emmanuel, a largely ultra-Orthodox settlement of a few thousand people, is located between Nablus and the West Bank town of Qalqiliya.

The armored bus was run by a private company and was traveling between the ultra-Orthodox town of Bnei Brak and Emmanuel, an Israeli security official said.

Armored ambulances and helicopters rushed to the scene to take the injured to hospitals. Israel Radio said helicopter gunships were also deployed to hunt for the attackers. Helmeted soldiers patrolled the area and the rocky valley below.

The bus itself appeared to be tilting on its right side, leaning toward a hill off the side of the road. Media and some rescue teams were initially prevented from reaching the scene because Israeli security officials feared other explosive devices might still be in the area.

“Once it is cleared, we will go in and take care of the bodies which are still there,” said Moshe Shapiro, a spokesman for an ultra-Orthodox group that recovers the remains of victims. “It is too dangerous at this stage to recover the bodies.”

Israel’s Channel Two television said the injured were not only from the bus, but from a vehicle that was driving ahead of it.

In more than 21 months of fighting, 1,758 people have been killed on the Palestinian side, and 572 on the Israeli side, including Tuesday’s attack.