Israel clamped an open-ended closure on the West Bank and Gaza Tuesday, banning virtually all Palestinians from Israel in a first response to a suicide bombing that killed five Israelis outside a shopping mall.

Israeli officials also said the army would target Islamic Jihad operatives in the West Bank, both through arrest raids and targeted killings of operatives, and renew airstrikes in the Gaza Strip in response to any Palestinian rocket attacks.

"We decided to operate in a much broader, much deeper and more intensive manner against the Islamic Jihad infrastructure, and I hope that we will be able to prevent such attacks in the future," Defense Minister Shaul Mofaz told Army Radio after a late-night meeting of security officials.

Monday's bombing in the coastal city of Netanya was the fifth since Israel and the Palestinians forged a cease-fire last February. Islamic Jihad has claimed responsibility for all five of them, saying its attacks are in response to Israeli violations of the truce.

The closure, which the army said would remain in effect indefinitely, prevented thousands of Palestinian merchants and laborers from reaching jobs in Israel, dealing a tough blow to the feeble Palestinian economy.

Gaza's main cargo crossing, however, remained open.

Israel has long demanded that the Palestinians rein militants as a condition for restarting peace talks. But so far Palestinian leader Mahmoud Abbas has preferred to seek dialogue with the armed groups, fearing confrontation could set off a civil war.

Early Tuesday, Palestinian security forces arrested three Islamic Jihad members in the northern West Bank — the area from which Monday's bomber came.

The arrests came after a call by U.S. Secretary of State Condoleezza Rice for the Palestinians to take action against militants. The U.S. ambassador to Israel echoed those remarks on Tuesday.

Israel "has every right to defend its people," Ambassador Richard Jones told reporters in Tel Aviv.

"We are doing everything we can to persuade the Palestinian Authority to shoulder its responsibility as a partner for peace," he said.

Islamic Jihad criticized the arrests. It said the men were low-level operatives and accused the Palestinian Authority of acting like Israeli security agents.

But Israel dismissed the gesture as insufficient.

"Arresting a few activists in a particular atrocity is simply not enough," said Mark Regev, spokesman for the Israeli Foreign Ministry. "This group has to be thoroughly disarmed. If not, they will continue to wreak havoc, murdering innocent civilians and killing the chance for peace."

With Palestinian legislative elections scheduled next month, a large-scale crackdown at the behest of Israel appears unlikely because it would weaken Abbas' Fatah movement, which faces a tough challenge from the larger Islamic group Hamas. Islamic Jihad is boycotting the election.

The Jan. 25 election could also temper the Israeli response, since violence could make Fatah appear ineffective and bolster Hamas.

The bombing could also reverberate in Israel, which is holding general elections in March. While Sharon faces pressure to respond to the suicide bombing, prolonged fighting could also hurt the prime minister, who recently left the hard-line Likud Party to form a party more amenable to peacemaking.

Both Sharon and Abbas, who condemned Monday's bombing, say they want to return to negotiations over the internationally backed "road map" peace plan.

Monday's attack was the third targeting the shopping mall in Netanya, nine miles from the West Bank.

Police and security guards spotted a man carrying a black bag and wearing a heavy sweatshirt outside the building and grew suspicious. A security guard pushed him away from a crowd waiting to get in, and the man blew himself up. The security guard was among the dead.

"If the bomber had gotten in, the result would have been much worse," said Israel's police chief, Moshe Karadi.