JERUSALEM (AP) Israel pressed its campaign of intense strikes throughout the West Bank and Gaza Strip yesterday, conducting sweeps in refugee camps and killing 12 Palestinians. A Palestinian suicide bomber attacked a West Bank settlement, while a gunman killed four people and wounded 20 in an Israeli settlement.

The attack on the Atzmona settlement came shortly after President Bush announced he planned to send his Mideast envoy back to the region.

A Palestinian gunman infiltrated the Gaza settlement late yesterday and killed four people, before soldiers shot him dead. The attacker wounded 20 people, five seriously, the Israeli military said.

Israel Radio reported the military wing of the militant Hamas organization claimed responsibility. The station said the infiltrator entered the Atzmona settlement from the south, near the Palestinian city of Khan Younis, and threw grenades as well as shooting.

Bush said he was sending Anthony Zinni to the troubled region next week in hopes of halting widening violence and called for both sides to end the fighting.

The president said the Israelis had to show "a vision for peace. There"s got to be more than security." Bush said, however, he fully supported Israel"s right to defend itself from Palestinian attacks.

He called on Palestinian leader Yasser Arafat to make a "maximum effort to end terrorism against Israel."

Israeli troops stormed through two West Bank refugee camps before dawn and rocketed a police station after nightfall in one of Gaza"s most crowded camps, sending Palestinian civilians running for cover. In the biblical West Bank town of Bethlehem, Israeli airstrikes on Palestinian leader Yasser Arafat"s local headquarters hit so hard they blew open bolted doors in nearby homes.

Israeli leaders said the campaign was aimed at forcing the Palestinians to stop terror attacks, but there was no sign of that yesterday.

News of Zinni"s departure came just hours after White House press secretary Ari Fleischer said the envoy would not be returning unless there was an "opening where a return by General Zinni would do some good."

Raanan Gissin, Israeli Prime Minister Ariel Sharon"s spokesman, said he would have no immediate comment on Zinni"s return. He said Israel was studying the development.

Palestinian negotiator Saeb Erekat welcomed the U.S. decision. "I do think its a useful move, and I do think that in the deteriorating situation it is necessary to have some serious intervention."

In the deadly conflict, a Palestinian suicide bomber walked into a Jewish settlement"s hotel complex and blew himself up in the lobby, injuring four people and sending canned goods and cereal boxes flying in the adjoining supermarket.

Another suicide bombing, at a trendy Jerusalem cafe, was thwarted when the cafe owner, a waiter and a customer jumped the man, shoved him outside and grabbed his bag after they saw wires dangling from it. "Who, me?" the man asked when confronted, cafe owner Gabi Aldoratz told Israel radio.

At a shopping center in Pardes Hanna, a city in Israel"s north, a resident spotted a suspicious object and called police. As a bomb disposal team approached, the bomb exploded, police said. No one was hurt.

Earlier yesterday, the Bush administration urged Israel to halt its widening assaults, saying they "work against the overriding objective of reducing violence and returning to negotiations."

"Such actions should be halted now," State Department spokesman Richard Boucher said.

Sharon, stung by an earlier rebuke from Secretary of State Colin Powell, responded that the conflict was "imposed on Israel by the Palestinian Authority and its leader."

"Israel has never declared war on the Palestinians. Israel fights back against terror organizations in the framework of its right of self-defense. He who started this war has the power to stop it, but continues to prefer a war of terrorism," Sharon"s office said in a statement.

On Wednesday, Powell said, "If you declare war on the Palestinians and think you can solve the problem by seeing how many Palestinians can be killed, I don"t know that leads us anywhere." Powell toned down criticism yesterday, saying Sharon should "be careful" of the means he uses in self-defense.

A defiant Arafat insisted Palestinians would not be cowed by the escalating strikes.

"No one can shake the Palestinians," he told reporters in the West Bank town of Ramallah yesterday, hours after Israel fired missiles at his headquarters complex for the third night in a row. "If the Israelis believe that they can frighten them by tanks or by missiles or by Apaches (helicopter gunships), then they are mistaken."

A suicide bombing that injured four Israelis, one of them seriously, took place at the entrance to Ariel, the West Bank"s second largest settlement. A radical PLO group, the Popular Front for the Liberation of Palestine, claimed responsibility.