TULKAREM, West Bank (AP) – A Palestinian suicide bomber trying to enter Israel blew himself up Thursday at a military checkpoint in the West Bank set up to foil the attack, killing an Israeli soldier and two other Palestinians.

The army said it had set up the checkpoint shortly after receiving warnings that a suicide bomber was headed toward Israel. The bomber was traveling in a taxi that was stopped at the roadblock for a security check.

After the vehicle was stopped, three occupants got out, including a man wearing a large overcoat. When soldiers ordered him to remove the coat, he detonated an explosives belt concealed beneath, the army said.

The suicide bombing took place just south of the Palestinian town of Tulkarem, about two miles inside the West Bank.

The army said the bomber, an accomplice and the taxi driver were killed. One Israeli officer died and three were wounded, one seriously, the army added. Palestinian ambulances took away an unknown number of wounded Palestinians.

The bombing came hours after Israeli warplanes and artillery pounded the northern Gaza Strip, beginning an aggressive new campaign to stop Palestinian rocket fire. The army has threatened to shoot anyone who approaches the border.

The Arabic satellite station al-Arabiya reported that Islamic Jihad claimed responsibility for the attack. The claim could not immediately be confirmed, though the Palestinian militant group earlier this week rebuffed an appeal from Palestinian leader Mahmoud Abbas to halt attacks on Israelis.

After the attack, the army imposed closures on the West Bank towns of Tulkarem and Qalqiliya, preventing people from coming in and out.

Israel’s deputy defense minister, Zeev Boim, said Thursday’s attack was carried out by Islamic Jihad operatives in the northern West Bank, with direct support from the group’s leadership in Syria.

“Their efforts to put suicide bombers in the center of Israel are always ongoing,” he told Israel Radio, praising the army for foiling what could have been a much worse attack if the attackers had reached an Israeli city. “This temporary checkpoint prevented a heavier catastrophe,” he said.

Islamic Jihad has carried out a series of suicide attacks since Israel and the Palestinians declared a cease-fire last February. It also has been responsible for most of the rocket fire out of Gaza aimed at southern Israeli towns, which has continued despite Israel’s withdrawal from the Gaza Strip in September.

Intent on halting the rocket attacks, Israeli artillery began imposing a new off-limits zone in northern Gaza, firing shells into the area to deter Palestinians from entering it.

The artillery fire late Wednesday and early Thursday marked the beginning of what the army said would be the biggest military operation since the Gaza pullout. Warplanes also struck roads used by militants to access the launching areas. Such airstrikes have gone on for weeks.

Vice Premier Ehud Olmert said the operation would be open-ended. Although no rockets were fired overnight, Olmert conceded the operation was unlikely to end the attacks altogether.

“I believe these means will drastically reduce the launchings,” he told Army Radio. “Nothing can totally prevent it unless those who fire will stop firing.”

Abbas has denounced the rocket fire and unsuccessfully urged Islamic Jihad to halt the attacks at a meeting on Tuesday, but he has condemned the tough Israeli response. Palestinian doctors said two Palestinians were wounded in the first hours of the operation.

Abbas is struggling to bring order to the chaotic coastal strip and the ongoing violence could weaken his appeal in Palestinian parliamentary elections next month, where the Islamic Hamas is mounting a stiff challenge.

There are no Palestinian villages in the buffer zone, which is mostly farmland. The Palestinian Interior Ministry said the no-go zone is about three miles long and about one mile deep.

The area includes abandoned Jewish settlements. Palestinian militants have taken advantage of the Israeli withdrawal to approach the border, increasing the range of their homemade rockets.

Over the last 10 days, two rockets have exploded in an industrial area south of the city of Ashkelon, where there are sensitive installations like a power plant and a fuel depot.

Israel has said it needed to take action because Abbas’ security forces have failed to do so.

In the latest sign of disorder in Gaza, Palestinian officials were trying to free a British aid worker and her parents, who were kidnapped by militants in the southern town of Rafah on Wednesday. It was not known who took them.

The human rights group Mezan confirmed that that the woman, Kate Burton, 25, has worked for the organization for four months. Officials said Burton was on vacation with her parents when they were abducted.

British officials said two diplomats were in Gaza working on the family’s release.

The abduction Wednesday was the latest in a string of kidnappings of foreigners in Gaza. In most cases, the kidnappers have sought jobs in the Palestinian security forces, the release of imprisoned relatives or other personal matters. In all cases, the victims have been released safely.