Israel has launched air-strikes at targets linked to the Islamic militant group Hamas in Gaza City, in response to the killing of a pregnant Jewish woman and her four daughters. Witnesses say several people have been injured. Observers say the violence could influence the outcome of a Likud Party referendum on a plan for an Israeli withdrawal from Gaza and parts of the West Bank.

An Israeli military helicopter fired three missiles at a 14 story-building in Gaza City that houses a radio station associated with Hamas and a Palestinian newspaper. Palestinian witnesses say that an official of Hamas was being interviewed at the time the missiles were launched. Part of the building's roof collapsed and residents say some of the tenants could be seen screaming from balconies for help.

Earlier, Palestinian gunmen ambushed a car on a road leading to the Jewish settlement in Gush Katif, killing an Israeli woman and her four children in a hail of gunfire.

Two Palestinian groups claimed responsibility, including the Islamic Jihad, listed by the State Department as a terrorist organization, and the Popular Resistance Committees, an umbrella group responsible for other attacks in the Gaza Strip.

But Israeli officials have placed the blame on Palestinian President Yasser Arafat and Hamas, another group that has carried out frequent suicide bombings and attacks that have killed dozens of Israelis.

Ranaan Gissin, a spokesman for Ariel Sharon, said the killing of the five Israelis was an attempt to sabotage the Israeli Prime Minister's plan to withdraw from the Gaza Strip and parts of the West Bank. "The fact that this attack was timed today clearly indicates that the terrorist organization, Hamas, which is actually implementing Arafat's strategy of terror, and Arafat, who is continuing with his strategy, really are fearful that this plan will go through because this plan is very good for Israel. It will allow us the degrees of freedom to fight against terrorism that we need and at the same time will prevent or will remove any excuse of not fighting terrorism of taking action against the terrorists," he said.

He spoke just hours before voting was to close at 443 polling booths across the country for nearly 200,000 eligible members of the Likud.

As voting got underway, Mr. Sharon made a final appeal to his party to vote in favor of his unilateral disengagement plan from Palestinian areas. He says that his plan is necessary to bolster Israel's overall security and a rejection by Likud members could place the nation's future at risk.