Israeli undercover troops hiding in a van loaded with vegetables killed a top Hamas militant in a roadside ambush Monday, and another group of soldiers blew up the house of a suspected Hamas bombmaker and fatally shot two Palestinians in a separate operation.

The military actions came as Israeli leaders pledged a crackdown on Hamas, the militant Islamic group that killed four soldiers in a weekend bombing of a tank in Gaza. Hamas has carried out many of the attacks against Israeli targets in the past 29 months of fighting, and says it will not stop despite renewed cease-fire talks between Israeli and Palestinian leaders.

The Israeli daily Haaretz said troops were poised for a major strike in Gaza, but would stop short of reoccupying the strip where more than 1 million Palestinians and about 7,000 Jewish settlers live.

"There will be no immunity, there will be no sanctuary, not in Gaza ... not in any other place," said Raanan Gissin, an aide to Israeli Prime Minister Ariel Sharon.

In all, 14 Palestinians were killed Sunday and Monday, most of them in the Gaza Strip. The dead included six Hamas members who died in a mysterious explosion Sunday. It remained unclear Monday whether the blast was caused inadvertently by militants handling explosives or if Israel targeted the group.

Tens of thousands of mourners attended their funerals Monday, and Hamas said it would step up attacks on Israel. "The crime against our fighters will not pass without ... punishment from Hamas and the Palestinian people," said Abdel Aziz Rantisi, a senior Hamas figure.

In the Israeli ambush Monday, troops emerged from a blue van loaded with vegetables as the Hamas militant Riyad Abu Zeid traveled in a black Honda along Gaza's coastal road. In an exchange of gunfire, the 32-year-old Abu Zeid was shot and seriously wounded, the army said. The Israeli troops seized Abu Zeid, who died as he was being taken by helicopter to an Israeli hospital, the army added.

A Palestinian taxi driver, who gave only his first name, Mohammed, said two Palestinian men in the Honda were hit in the shooting, and an Israeli military ambulance took them away. One was apparently killed at the scene and the other was wounded, he said. The Honda's windshield was riddled with bullet holes, and blood covered the front passenger seat. The second man was believed to be a bodyguard for Abu Zeid, but his name and condition were not known.

The army described Abu Zeid as a senior member of Hamas' military wing who had organized attacks against Israeli targets in the Gaza Strip and suicide bombings in Israel. He was planning additional attacks, the army said, without giving details.

In the other Israeli military operation in Gaza, about 35 tanks, escorted by helicopter gunships, entered the Sheik Radwan neighborhood in Gaza City early Monday.

Troops surrounded the five-story family home of Ahmed Ghandour, a top aide to Hamas bombmaker Adnan al-Ghoul. Israel believes Ghandour, who remains in hiding, was responsible for planning the weekend attack on the Israeli tank.

Troops ordered everyone out of the targeted building and adjacent homes and took the men away, witnesses said. Then soldiers sent dogs inside to see if anyone was left behind. Neighbors were ordered to leave their windows open to help absorb the shock of the explosion, which flattened Ghandour's house and damaged several surrounding homes.

During the five-hour incursion, Palestinian gunmen attacked Israeli soldiers, who returned fire, the army said. A Palestinian policeman and a suspected militant were killed, hospital officials said. Five civilians, including a doctor, were reported wounded.

Israel has been blowing up houses of suspected militants in an attempt to deter militants from attacking Israelis. Palestinians and human rights groups charge such actions violate international law and constitute collective punishment.

The violence erupted amid new efforts to negotiate a cease-fire. Israel and the Palestinians sent delegations to London on Monday to meet with members of the so-called Quartet of Mideast mediators -- the United States, the European Union, the United Nations and Russia.

On Sunday, Sharon met with Palestinian Finance Minister Salam Fayad, his second session with senior Palestinian officials in recent days after a long freeze in contacts.

Fayad, in a telephone interview from London, said he met with Sharon to discuss financial issues, including the transfer of tax money collected by Israel for the Palestinian Authority.