Israel has launched air strikes in the Gaza Strip for the fourth straight day, with the aim of stopping Palestinian rocket attacks. The offensive may have helped Prime Minister Ariel Sharon win a vote of confidence in his ruling Likud party.

Israeli aircraft fired missiles at bridges, roads, and buildings in Gaza, as Israel kept up the pressure on Palestinian militants. Troops detained more than 90 militants in the West Bank, bringing the total of arrests this week to around 400.

The offensive continued into its fourth day, despite a declaration from the Islamic group Hamas that it is stopping the rocket attacks that sparked the Israeli raids. Hamas leader Mahmoud al-Zahar.

"We are calling our militant group to stop their activities against the Israeli occupation outside Gaza Strip," said Mahmoud al-Zahar.

But Israel was not impressed, especially since Hamas claimed responsibility for kidnapping and killing a 50-year-old Israeli man in the West Bank. Also, smaller militant groups like Islamic Jihad have not agreed to stop firing rockets.

Defense Minister Shaul Mofaz told Israel Radio that there are new rules of engagement, now that Israel has pulled out of Gaza.

"We will hit them and hit them and hit them, until Israeli children can sleep in peace," Mr. Mofaz said.

Israel's tough response may have helped Prime Minister Ariel Sharon fend off a revolt in his hawkish Likud party. Former Prime Minister Benjamin Netanyahu wanted to oust Mr. Sharon as party leader because he defied the Likud by dismantling 21 Gaza settlements. But Mr. Sharon narrowly won a vote of confidence that put off elections for the Likud leadership until April of next year.

Mr. Netanyahu vowed to continue the struggle.

He said his supporters would oppose any plans by Mr. Sharon to withdraw from territory in the West Bank.