Israeli Prime Minister Benjamin Netanyahu said the "blood of Israeli civilians" would not go unpunished as he vowed to hunt the killers of four Israelis near a Jewish West Bank settlement.
"We witnessed today a savage murder of four innocent Israelis," Netanyahu said in Washington on Tuesday, where he was due to resume direct peace negotiations with the Palestinians on Thursday for the first time since December 2008.
"There are seven new orphans that were added to the circle of grief in Israel," he said, before going into talks with US secretary of state Hillary Clinton. "We will not let the blood of Israeli civilians go unpunished.
"We will find the murderers, we will punish their dispatchers," Mr Netanyahu said. "We will not let terror decide where Israelis live or the configuration of our final borders."
The military wing of the Islamist movement Hamas, which controls the Gaza Strip, said it was behind the killings.
Earlier, in a statement relayed to reporters by staff travelling with Mr Netanyahu, the Israeli Prime Minister ordered his security forces to hunt for the killers "without diplomatic restraint."
The move appeared designed to give Israeli security forces the freedom to search for the attackers in the Palestinian West Bank, despite the resumption of the high-profile peace talks in Washington.
Using the plane's telephone, the Prime Minister was briefed on the attack that took place near a West Bank Jewish settlement by defence minister Ehud Barak and the head of the Shin Beth security service, Netanyahu's staff said.
Mr Netanyahu said the killings underlined the security guarantees that Israel would need as he begins direct peace negotiations with Palestinian leader Mahmud Abbas hosted by Clinton.
"These and other issues will be determined in negotiations for peace that we are conducting," Mr Netanyahu said. "In these negotiations, I will set clearly the security needs that are required precisely to address these kind of terror, and I hope to have the opportunity to go into greater detail with my conversations with President (Barack) Obama tomorrow and with secretary Clinton today and with the leaders of Egypt, Jordan and Palestinians as well."
Ms Clinton reiterated an earlier US condemnation of the attacks and offered fresh security assurances to the Israeli people as she went into talks with Mr Netanyahu.
"This kind of savage brutality has no place in any country under any circumstances," she said.