RAMALLAH, West Bank ? Israel called up reserve soldiers Thursday and detained many Palestinian men and youths for questioning after troops entered Palestinian towns in a widening military response to a wave of suicide attacks.

After nightfall, suspected Palestinian infiltrators took hostages in a house in the West Bank settlement of Itamar, near the city of Nablus, killing four Israelis and wounding at eight others, settlers and rescue workers said.

The casualties were from one family except for an Israeli soldier, who was wounded when the military stormed the house. One of the infiltrators was also killed and the other fled out a window, the settlers and rescuers said.

The Popular Front for the Liberation of Palestine took responsibility for the attack in a call to The Associated Press.

The Israeli government’s decision to seize some Palestinian territories was a direct response to repeated suicide attacks. Two bombings in Jerusalem killed 26 Israelis on Tuesday and Wednesday.

Israeli forces set up tents in some Palestinian areas, indicating a plan to stay for at least a few days, but were not building permanent infrastructure like water pipes or electricity lines.

Defense Minister Binyamin Ben-Eliezer said one reserve unit, or about 1,200 troops, were called up to bolster Israel’s defenses.

“This call-up is meant to give backup to the standing army so it can face a new strategic situation in the (Palestinian) territories,” he told Israel TV.

Military sources said their scheduled reserve duty had been brought forward with special orders, and they would be deployed along the line between the West Bank and Israel. In March, ahead of Israel’s largest-scale military operation in a generation, Israel called up about 20,000 reserve troops.

The call-up came as the army rounded up Palestinians in Jenin, Qalqiliya, Bethlehem and Beitunia, a suburb of Ramallah. Israeli forces tightly encircled Tulkarem, as Israel Radio broadcast alerts about suicide bombers about to attack Israel.

Since taking control of the Jenin refugee camp late Tuesday, Israeli soldiers have been going from house to house, guided by maps, detaining about 2,500 men and boys, hauling them away in buses for questioning, Palestinians said. About 1,000 were released Thursday. The Israeli military would say only that soldiers detained Tarek Izzedine, 28, a local leader of the Islamic Jihad group, which has claimed responsibility for suicide attacks..

After a two-day sweep, Israeli forces pulled out of Qalqiliya, which is on the line between Israel and the West Bank at Israel’s narrowest point, where the country is just nine miles across. Attention shifted to Tulkarem, also on the unmarked line but nine miles to the north, where police and army reinforcements patrolled, looking for a bomber.

The suicide bombings delayed plans by President Bush to deliver a speech outlining U.S. recommendations for Mideast peacemaking. White House press secretary Ari Fleischer said Bush first wants to see Palestinian leader Yasser Arafat carry out his pledges to fight terror. “The progress the president is looking for is action,” Fleischer said.

Bush called Israeli Prime Minister Ariel Sharon on Thursday. Fleischer said “most of the conversation was about condolence and sympathy for what Israel is going through.” Also, Secretary of State Colin Powell talked to the foreign ministers of Egypt, Jordan and Saudi Arabia.

Sharon, speaking at a session of the three-day Zionist Congress in Jerusalem on Thursday, said, “The destruction of terror and the complete cessation of violence are the preconditions for any possibility of achieving peace.”

Ben-Eliezer, the defense minister, came out strongly against his government’s new policy, announced Wednesday, of retaking West Bank areas slice by slice until terror attacks stop. “I am completely against all permanent seizure of territories. I didn’t agree in any forum to punitive occupation,” he told Israel Radio.

Ben-Eliezer leads the moderate Labor Party, which is teamed with Sharon’s hawkish Likud in a broad-based coalition government.

He said he opposed reinstituting Israeli civilian control over Palestinians, the arrangement that was in place before the 1994 interim peace accords. Under the accords, Israel turned control of Palestinian cities, towns and most villages over to the newly created Palestinian Authority.

Ben-Eliezer’s Labor Party colleague, Foreign Minister Shimon Peres, agreed. “We are against reoccupying territory,” he told Israel TV’s Channel 10. “We are against the dissolution of the Palestinian Authority. We are in favor of preventive actions, where they are possible.”

In contrast, some of Sharon’s party faithful have been pressing for harsher measures, including the reoccupation of all of the West Bank and the expulsion of Arafat.

Arafat released a statement Thursday condemning the suicide bomb attacks but did not appeal to his people in person or on television, as aides had said he would. The statement was less explicit than earlier ones, in which he labeled the suicide bombings terrorism.

Speaking to reporters in English, however, Arafat denounced “terrorist activity against innocent people, Israeli or Palestinian civilians.”

In his Arabic statement, Arafat said shootings and bombings “must be completely halted.” Otherwise, he warned, the result might be “full Israeli occupation of our lands.”

But Palestinian security chiefs said no arrests would be made as long as Israeli forces occupied Palestinian areas.

The extremist Hamas group, meanwhile, pledged to continue the bombing campaign.

“If we have an effective weapon in our hands and the whole world is trying to take it off us, this kind of reaction shows it to be the most effective way,” said Ismail Abu Shanab, a Hamas spokesman in the Gaza Strip.

Hamas claimed responsibility for the Tuesday bus bombing in Jerusalem that killed 19 Israelis, the deadliest in the city in six years.