By Eli Berelzon
BANI NAIM, West Bank (Reuters) - Four Israeli settlers were shot dead in their car in a drive-by attack in the occupied West Bank on Tuesday, on the eve of a U.S.-sponsored Middle East peace summit in Washington.
The armed wing of the Islamist Hamas movement, the Islamist group which controls the Gaza Strip and opposes peace talks, claimed responsibility for the shooting in a statement.
"This was a terrorist attack and the army is treating it as a grave incident," Israeli Army spokeswoman Lieutenant Colonel Avital Leibovitch told reporters in a telephone briefing. She said two men and two women, one pregnant, had been killed.
Army sources said all four victims were Israelis from the Beit Haggai settlement.
"The Qassam Brigades announces its full responsibility for the heroic operation in Hebron," said a statement from Hamas armed wing Izz el-Deen al-Qassam.
The claim confounded recent Hamas signals that it did not want militants to rekindle the attacks on Israel that triggered a devastating Israeli military assault in the winter of 2008-09 in which 1,400 Palestinians and 13 Israelis lost their lives.
Tuesday evening's shooting was the most lethal attack in the West Bank in four years, the Army said. A suicide bombing killed four Jews at a West Bank settlement in 2006. In Jerusalem two years ago eight Jews were killed at a seminary.
Defense Minister Ehud Barak said Israel would "exact a price" for the killings.
"This was an apparent bid by lowly terrorists to sabotage the attempt to achieve a diplomatic process and to try to hurt the chances of the talks opening in Washington," he said in a statement.
Hamas rejects the Palestinian leadership in the West Bank and opposes the direct peace talks due to resume formally in the U.S. capital on Sept 2.
"Hamas praises the attack and regards it as a natural response to the crimes of the occupation," Sami Abu-Zuhri, a Hamas spokesman in Gaza, said before the claim of responsibility was issued.
BUSY HIGHWAY FOR BOTH
The four Israelis were shot in their vehicle near Bani Naim, close to the flashpoint West Bank city of Hebron, which has seen violence for decades but has been quiet for some months. Israeli settlers live in a tiny enclave in the city amid Palestinian residents, under the close protection of Israeli army forces.
The attack took place after dark on Highway 60, a busy route used by both Palestinians and Israeli settlers.
The United States and its allies in the search for a Middle East peace treaty have urged all parties to refrain from any action that could disrupt the resumption of direct negotiations after a hiatus of 20 months.
Israelis and Palestinians alike have predicted that opponents of a peace deal would try to derail the talks through violence, as in the past.
State Department spokesman P.J. Crowley told reporters in Washington: "We ... are cognizant that there may well be actors in the region who are deliberately making these kinds of attacks in order to try to sabotage the process."
U.N. Special Coordinator for the Middle East Peace Process Robert Serry urged "all parties not to allow the enemies of peace to derail the negotiations about to be launched."
"We condemn this murderous act and call for those responsible to be brought to justice," he said in a statement.
Israeli army spokeswoman Leibovitch said: "Security was stable for the past few years and we hope this will not cause any deterioration."
ISLAMISTS HAIL ATTACK
Hamas spokesman Aub-Zuhri said the attack was proof "of a failure of security coordination" between Israel and the Palestinians -- a reference to the Western-backed Palestinian Authority whose U.S.-trained forces have been credited with suppressing armed militants in their territory.
The Israeli and Palestinian leaders, Prime Minister Benjamin Netanyahu and President Mahmoud Abbas -- were due to meet U.S. President Barack Obama for dinner at the White House on Wednesday and open formal talks on September 2 -- their first direct negotiations after talks broke off in late 2008.
The Palestinians are split, with Hamas condemning the talks as a sell-out. Abu Ubaida, a spokesman for Hamas's armed wing called the attack "a natural response to the crimes of the occupiers, an evidence of the presence of resistance despite of the war of liquidation."
Speeches from loudspeakers at a mosque in the northern Gaza Strip celebrated news of the attack.
Israeli Education Minister Gideon Saar, a close ally of Netanyahu, told Israel's Channel 10 television that "no prize should go to the murderers" by putting off talks.
"It is very regrettable how -- not for the first time -- against the background of diplomatic talks aiming to advance peace, the nearly automatic response of Palestinians was a terrorist attack on civilians," Saar said.
(Reporting by Alyn Fisher-Ilanin Jerusalem and Nidal al Mughbrabi in Gaza; Writing by Douglas Hamilton; Editing by Peter Graff)