NETANYA, Israel – A Palestinian suicide bomber blew himself up outside a shopping mall in this seaside town yesterday, killing three other people, injuring dozens more, and shattering a long stretch of comparative calm in the weeks before Israel’s expected pullout from the Gaza Strip.

The early-evening attack was the first of its kind since the end of February and battered an already shaky truce declared that month by Palestinian Arab militant groups, which agreed to observe a period of quiet up through Israel’s evacuation of Jewish settlements in Gaza and the northern West Bank.

Israeli and Palestinian Arab officials quickly condemned the blast, describing it as an attempt to disrupt the withdrawal, scheduled to begin in the middle of next month.

“Once again we return to the same sights [of carnage],” Israel’s deputy minister of internal security, Yaacov Edri, told reporters at a hospital where some of the wounded were taken. “It’s unbelievable, but we knew that there would be those who would try to sabotage the disengagement process.”

The Israeli government has insisted that it will not carry out its “disengagement” plan under fire from Palestinian Arab radicals, but officials said yesterday that the pullout would go on as planned.

“Those who stand behind [the attack] are working against the Palestinian people. No sensible person can do such things on the eve of the withdrawal from Gaza and the northern West Bank,” the president of the Palestinian Authority, Mahmoud Abbas, said. He promised harsh punishment for those behind the attack.

A wing of the militant group Islamic Jihad claimed responsibility, calling the attack retaliation for Israel’s continued pursuit of its members. But as of late yesterday, the organization’s central leadership had not put out a formal statement affirming its involvement, as is customary with the group.

Still, of the main Palestinian armed factions, Islamic Jihad had long been considered the most likely to ignore the informal cease-fire because of its hardline stance against Israel, its ties to Iran and Lebanon, and its loose command structure that allows maverick cells to mount their own operations. The last suicide bombing, which killed five people outside a Tel Aviv nightclub on February 25, was the work of Islamic Jihad.

Yesterday’s bomber was identified as 18-year-old Mustafa Ahmed abu Khalil from the West Bank village of Atil, about 10 miles west of Netanya. The Al Jazeera satellite news channel aired a farewell videotape by Khalil in which the young man vowed vengeance against Israel.

There were also reports last night that Israeli forces had moved into Khalil’s community and the neighboring Tulkarm, sealing off entrances to a city that was handed over to Palestinian control just four months ago.

Earlier yesterday, about 7 p.m., Khalil was among a knot of pedestrians crossing the street in front of the popular Sharon mall in Netanya, a coastal resort town. In the middle of the crosswalk, he detonated an explosive belt, spraying blood and flesh and radiating a flash of intense heat.

“I felt like a ball of fire was coming down from the sky. We weren’t sure what happened, and we ran into the mall,” said Adi Menashe, 16, who was heading into the shopping center to buy some balloons. “I saw people lying there. One lady had caught on fire.”

Two women were declared dead at the scene, a third victim died soon afterward, and the number of injured topped 60.

No large-scale retaliation by Israel is expected, in part because the government is scrambling to get ready for next month’s Gaza pullout and because the other Palestinian militia groups, such as Hamas, have signaled their willingness to abide by the cease-fire.

But Israeli officials repeated their demands that Mr. Abbas disarm the radicals, something the Palestinian leader has been loath to do for fear of igniting civil war among feuding factions, including his own Fatah party.

A meeting scheduled for yesterday evening among Israeli, Palestinian, and American officials to discuss the withdrawal plan was canceled following the blast. Besides the Netanya attack, Islamic Jihad also appeared responsible for an unsuccessful car bombing just minutes before in the West Bank Jewish settlement of Shavei Shomron.