Israel (search) pressed forward with a broad offensive against Islamic terrorists on Sunday, killing an Islamic Jihad (search) commander in a pinpoint airstrike in the Gaza Strip (search) and rounding up more than 200 wanted Palestinians.

Prime Minister Ariel Sharon promised to use "all means" against the militants, and Hamas (search) later said it would halt rocket fire. Early Monday, the Israeli military carried out two airstrikes in Gaza.

The offensive, coming just two weeks after Israel withdrew from Gaza, followed a wave of militant rocket attacks against Israeli towns over the weekend. Israel has promised to continue with its airstrikes, arrests and a possible ground invasion until the rocket fire ceases.

"There shall be no restrictions on the use of all means to hit the terrorists and the terror organizations, their equipment and their hideouts," Sharon told his Cabinet Sunday.

Despite the pledge from Hamas, Israeli officials said they would wait to see if things remained quiet before calling off the offensive.

The pullout and the recent wave of fighting have weakened Sharon in his ruling Likud Party ahead of a crucial vote Monday. Sharon walked out of a stormy Likud meeting Sunday without delivering his prepared speech after what appeared to be an intentional electricity outage prevented him from speaking.

Many party members are angry at Sharon over the pullout, and it appeared that his opponents sabotaged the electric system. Monday's vote will set a date for party primaries, and a setback for Sharon could force him to leave the party he founded three decades ago, most likely to form a new centrist party.

Early Monday, an Israeli helicopter fired a missile in an attack the army said was aimed at a road in Gaza leading to a field used by militants to fire rockets at Israel. In another attack early Monday, an Israeli helicopter fired two missiles at a workshop the army said was used by Hamas to make weapons.

That airstrike in Gaza City set the building on fire, but no casualties were reported in either Monday attack.

Sunday's airstrike killed Islamic Jihad's top commander in southern Gaza, Mohammed Khalil, and his bodyguard as they drove along a coastal road in Gaza City.

The airstrike signaled a return to Israel's policy of targeted killings, which were halted after a February cease-fire declaration.

The army said Khalil, 35, was responsible for attacks that killed 17 Israelis.

After the airstrike, Mohammed al-Hindi, Islamic Jihad's top leader in Gaza and the West Bank, said the group would no longer honor the cease-fire. "There is no talk of a truce, there is only room for talk of war," he said.

Although the truce has brought a sharp drop in fighting, Islamic Jihad has carried out a series of attacks in recent months, including three suicide bombings in Israel.

However, Mahmoud Zahar, leader of the much larger Hamas group, said he had ordered an end to rocket attacks and a halt in military-style celebrations in order to preserve the truce.

"We call on our military groups to stop their operations against the enemy from the Gaza Strip," he told a news conference.

The latest violence erupted after a blast killed 20 people at Hamas military parade celebrating the Gaza pullout last Friday. Hamas blamed Israel, but the Palestinian Authority said the explosion was caused by the mishandling of explosives. Israel, which usually acknowledges attacks on militants, denied involvement in the blast.

Hamas responded by firing nearly 40 rockets into Israel, sparking the Israeli offensive. Hamas has been under pressure from Palestinian officials and Egyptian mediators to end the violence.

Late Sunday, Palestinian gunmen opened fire at the Gaza home of Tawfiq Abu Khoussa, spokesman for the Palestinian Interior Ministry, the agency in charge of Palestinian security.

Abu Khoussa declined to say who was behind the shooting, but hinted Hamas was involved. Hamas has criticized Abu Khoussa and other officials for saying that negligence caused the blast at last week's rally.

The fighting has destroyed the lingering atmosphere of goodwill after the Gaza pullout and increased pressure on Palestinian leader Mahmoud Abbas to confront militants. Abbas has refused to use force against militants, preferring instead to co-opt them by inviting Hamas to run in upcoming legislative elections.

Mark Regev, spokesman for the Israeli Foreign Ministry, said there can be no progress in peace talks until Abbas disarms militant groups. "As long as extremists have the ability to torpedo the process of reconciliation and to launch attacks, we will be at their mercy," Regev said.

Abbas said Sunday that he asked U.S. officials to pressure Israel to pull back from its offensive. "We're back to square one. Now we need time to regain calm. Our people need a quiet life and to make a living," he said.

U.S. Secretary of State Condoleezza Rice spoke with Israeli and Palestinian leaders over the weekend to prevent the situation from further deteriorating, American and Palestinian officials said.

"We understand the terrorists are trying to provoke Israel at this sensitive time, we understand the Israeli position and the response it has taken," said Richard H. Jones, the U.S. ambassador to Israel.

Early Sunday, Israel arrested 207 wanted Palestinians in the West Bank, most of them members of Hamas and Islamic Jihad.

Meanwhile, Israeli troops, backed by armored bulldozers, tanks and armored personnel carriers, massed outside Gaza. Israel set up five artillery pieces on the border, and fired test-rounds into empty fields in northern Gaza to calibrate their guns in preparation for a possible artillery assault. There were no injuries.

In the past, Israel retaliated against Palestinian rocket fire with air strikes or ground incursions, but not artillery fire, which is imprecise and could cause many casualties in densely populated Gaza.