JERUSALEM -- A Palestinian gunman opened fire Tuesday on an Israeli vehicle in the West Bank and killed four passengers on the eve of a new round of Mideast peace talks in Washington. The Islamic militant group Hamas praised the shooting.

There was no immediate claim of responsibility. But in the past, militant groups have staged attacks in an effort to sabotage peace efforts.

Police spokesman Micky Rosenfeld said the gunman opened fire at a vehicle traveling near Hebron -- a volatile city that has been a flash point of violence in the past. Some 500 ultranationalist Jewish settlers live in heavily fortified enclaves in the city amid more than 100,000 Palestinians.

Israel's national rescue service said the victims were two men and two women. It gave no further details. Israeli media reported that one of the women was pregnant and that the dead ranged in age from mid-20s to mid-40s. The reports said everyone in the car was killed.

The attack occurred as Israeli Prime Minister Benjamin Netanyahu was en route to Washington for a White House summit launching peace talks on Wednesday. Palestinian President Mahmoud Abbas was already in the U.S. capital meeting with U.S. Secretary of State Hillary Rodham Clinton.

More On This...

President Obama hopes to forge a peace agreement within one year.

Asked about the shooting, State Department spokesman P.J. Crowley said the U.S. is aware "there are those who will do whatever they can to disrupt or derail the process."

There is widespread opposition to the resumption of the peace talks among Palestinians. Hamas, which rules Gaza, opposes any contact with Israel and has harshly criticized Abbas for agreeing to resume the negotiations.

Hamas is considered a terrorist group by the U.S., Israel and European Union and is the main rival of Abbas and his Fatah movement. Hamas expelled Fatah forces from Gaza in its violent takeover in 2007.

In a statement, Gaza Hamas spokesman Sami Abu Zuhri said the group "praises the Hebron operation." He did not claim responsibility or mention the peace talks.

Netanyahu, leader of a hard-line coalition of religious and nationalist parties, has said that protecting Israel's security interests will be his top priority as he negotiates with the Palestinians.
Before leaving for Washington, Netanyahu told his Likud Party that he would seek "real arrangements on the ground" that ensure the security of Israelis.

"True peace is not a short break between wars, it's not a short break between terror attacks. True peace is something that persists dozens of years, that stands well for generations," he said.

Education Minister Gideon Saar, a member of Netanyahu's Likud Party, denounced the shooting. "This is not the first time, especially with peace talks in the background, that the automatic Palestinian reaction is terror attacks against Israelis," he told Israel's Channel 10 TV.

The attack disrupted a relative lull in the West Bank. The last fatal attack occurred in June, when Palestinians opened fire on a police vehicle near Hebron and killed one officer.

It was the deadliest Palestinian attack against Israelis since March 2008, when a lone attacker gunned down eight students in a Jerusalem rabbinical seminary.

Opposition to resuming talks is also coming from within the Palestine Liberation Organization, an umbrella group headed by Abbas. Some Fatah activists threaten to try to depose him if he makes concessions, and several hard-line PLO groups plan a demonstration in the West Bank administrative capital of Ramallah on Wednesday to protest resumption of negotiations.

A previous U.S. launching of Israeli-Palestinian peace talks was also accompanied by deadly violence. Palestinian gunmen shot and killed an Israeli in the West Bank before then-President George W. Bush convened Israeli and Palestinian leaders for a summit in Annapolis, Maryland, in November 2007. The gunmen said the attack was "an act of protest against the Annapolis conference."

Talking to reporters on his plane heading for Washington, Abbas called for decisive American involvement in the talks.

He said that if the two sides reach a deadlock, the Obama administration should "present bridging proposals to bridge the gap between the two positions."

In one major challenge to the first direct talks between the sides in two years, Abbas warned it would be difficult to continue negotiating if Israel fails to extend a 10-month curb on West Bank settlement construction that ends in late September. Netanyahu has not made a final decision.