But identifying those responsible may prove difficult. Despite early reports, both Islamic Jihad and the Al Aqsa Martyrs Brigade, two of the most active Palestinian militant groups, denied involvement in the attack. Other observers speculated that Lebanon-based Hezbollah was behind the bombing. Israel accuses the Shiite Muslim extremist group of instigating and financing many Palestinian attacks.
In the past, militant groups have been quick to take responsibility for bombings. In this case, no group has rushed to claim the attack.
"We are committed to the quiet. We have no relationship to what happened tonight," Mohammed Hindi, a spokesman for Islamic Jihad, told the Arabic news channel Al Arabiya.
In Washington, Secretary of State Condoleezza Rice, who visited Israel and the West Bank this month to promote the peace process, called on the Palestinian Authority to "take immediate, credible steps to find those responsible for this terrorist attack and bring them to justice.... We now must see actions that send a clear message that terror will not be tolerated."
In recent weeks, Israel made a number of conciliatory gestures, including the release of 500 Palestinian prisoners, a dramatic scaling back of military operations in the West Bank and Gaza Strip, and a halt to its much-criticized policy of demolishing homes belonging to the families of suicide bombers.
Despite the lull, several Palestinians have been killed in various incidents, including one who was shot to death Friday in Gaza by Israeli soldiers.
Sharon also offered to return some West Bank towns to Palestinian control, but those talks hit snags. Friday's bombing was likely to further delay the Israeli pullback, even though no large-scale military retaliation was planned, Israeli media said.
"We will have to examine ourselves and see where we need to tighten the screws, and the Palestinians, too, will have to see where they need to do the same," said Gideon Ezra, the Israeli minister for public security. "We will not let this attack slide. And what the Palestinians are doing at the moment is insufficient."
Palestinian officials reject such complaints, saying their security infrastructure in the West Bank has been devastated by the continuing presence of Israeli soldiers and tanks.
