Israeli aircraft fired missiles Thursday night at a car carrying members of the Palestinian militant organization Islamic Jihad in the northern Gaza Strip, killing all four men inside the vehicle and three civilian bystanders.
One of those in the car was identified as a senior Islamic Jihad commander. The dead bystanders included two teen-agers, and about a dozen other people were hurt, Palestinian medical officials said.
The Israeli raid, which came the day after a suicide bomber sent by Islamic Jihad killed five Israelis in a crowded, open-air market, signaled the start of what Israeli Prime Minister Ariel Sharon described as a wide-ranging and open-ended offensive against Palestinian militant organizations -- and Islamic Jihad in particular.
One of those killed in the missile strike in the Jabaliya refugee camp was identified by Palestinian sources and the Israeli army as Shadi Mohanna, a prominent member of Islamic Jihad's military wing in Gaza.
The Israeli army said he was "responsible for several murderous attacks."
Hours earlier, Israeli troops in jeeps backed by combat helicopters pushed into the volatile West Bank town of Jenin and arrested a top local leader of Islamic Jihad.
Israel said the offensive was triggered by Palestinian Authority President Mahmoud Abbas' failure to act resolutely to prevent attacks against Israelis by militants.
Palestinian officials said that by increasing the daily hardships of ordinary Palestinians in the West Bank and Gaza Strip, Israel risked creating a climate in which the militant groups' popular political backing will grow.
Arrested in the Jenin raid was Abdel Halim Izzadine Haia, identified by Israeli authorities as a local commander of the group.
Haia was reported to have been on the phone with an Israeli television journalist, discussing in detail the implications of the previous day's suicide bombing, when troops surrounded his home.
Five other suspected members of Islamic Jihad were arrested in Jenin along with Haia, Israeli media reported.
Israeli security officials indicated that military operations in coming days and weeks would be centered on Gaza and a large swath of the northern West Bank. The latter area includes Jenin and Tulkarm, headquarters of the Islamic Jihad cell believed responsible for Wednesday's market bombing in the northern Israeli coastal city of Hadera.
In concert with its pullout of troops and settlers from the Gaza Strip, completed last month, Israel relinquished a small portion of the northern West Bank, uprooting four Jewish settlements.
Thousands of mourners turned out Thursday for the funerals of the five bombing victims, most of whom were older shoppers.
One was an Arab citizen of Israel; another had emigrated from Uzbekistan a dozen years earlier.
An elderly couple, Aharon and Sabiha Nissim, who lived on a collective farm, became separated while shopping, Israeli media said.
When he heard the explosion, Aharon Nissim looked for his wife. He remembered that she was particularly fond of the falafel that was sold at a stand at the market's entrance.
He found her lying on the ground mortally wounded near the stand, where the suicide bomber had struck apparently because of the long line of patrons gathered there. Nissim cradled his 66-year-old wife in his arms as an ambulance rushed her to a hospital, knowing that she was already dead or dying.
"We are simple people," the Israeli newspaper Haaretz quoted him as saying.
About 20 people remained hospitalized a day after the attack, Israeli authorities said.
Sharon, speaking before a meeting with Russian Foreign Minister Sergei V. Lavrov, said military actions in response to the Hadera bombing would be "broad and unstinting, until they halt terrorism."
Israeli military officials likened the offensive to a large-scale West Bank invasion in spring 2002, albeit on a smaller scale. During that time, troops seized nearly every major Palestinian town and city. Hundreds of Israelis and Palestinians died in the fighting.
The current operation will impose tight restrictions on Palestinians' movements, perhaps lasting months, the officials said. Palestinian officials expressed frustration, saying harsh measures affecting civilians would only inflame tensions.
"We have condemned the Hadera attack," Palestinian Authority Prime Minister Ahmed Korei told reporters in the West Bank city of Ramallah. "But at the same time, we condemn Israeli aggression. This aggression doesn't ensure calm."
Before dawn Thursday, Israeli troops arrested the father of Hassan abu Zeid, the 20-year-old Hadera suicide bomber from the village of Kabatiya, near Jenin. The family said the young man left the family home for prayers hours before the attack and did not return.
Special correspondent Fayed abu Shammalah in Gaza City contributed to this report.