In the southern Gaza Strip, Israeli helicopters fired missiles at two cars, killing six Palestinians and injuring five, Palestinians said. Four of the dead belonged to the militant group Hamas, the movement said. The Israeli military said it targeted and killed Yasser Rizik, a "senior Hamas activist" who was behind a January attack that killed four soldiers.
Israeli security sources confirmed the Gaza attack was part of Israel's policy -- condemned internationally -- of killing militants it blames for suicide bombings and shooting ambushes during a 21-month-old uprising against Israeli occupation.
"The Israeli assassins must be punished to deter them from repeating such an ugly crime," Mahmoud al-Zahar, a senior Hamas official, told Reuters. "The answer...will be the continuation of resistance and jihad (holy war) by all means available."
Also in Gaza, Palestinian police surrounded the house of Hamas spiritual leader Sheik Ahmed Yassin, and Palestinian authorities said he was under house arrest. But with Hamas enjoying strong grass-roots support, it was unclear how effective the measures would be. Palestinian police kept their distance from Yassin's house, which was ringed by dozens of armed Hamas members on Monday, witnesses said. About 40 Hamas supporters threw stones and bottles at the police, who fired into the air to quell the crowd.
One man was shot and wounded when police broke up a march by dozens of Hamas supporters near Yassin's house, Hamas members and hospital officials said.
Police said the Hamas supporters opened fire, but the protesters said the police has started the shooting.
The Palestinian Authority last imposed house arrest on Yassin in December, but Israeli officials dismissed it as a ploy and restrictions on his movements were gradually lifted.
Hamas is sworn to Israel's destruction and its militants have claimed responsibility for suicide attacks which have killed scores of Israelis.
The latest turbulence came as both sides awaited an address by President Bush, who was expected to propose a fresh start for peacemaking and offer guidelines for a future Palestinian state. Mr. Bush put off the speech last week because of the escalating violence, which included three major Palestinian attacks that left more than 30 Israeli civilians dead, and prompted the Israeli invasion.
In Washington, there's been widespread speculation that Mr. Bush's plan will call for a provisional Palestinian state. The details are not known, though the idea has been flatly opposed by Israeli Prime Minister Ariel Sharon, while Arafat and his aides have given it a cool reception
Mr. Bush faces a debate within his administration over what Palestinians should be required to do to win the statehood they seek in the West Bank and Gaza Strip.
A declaration of U.S. support for an interim Palestinian state while details of a final peace agreement are negotiated has been put forward as one option Bush might pursue.
Sharon said last week that the time was not "ripe" for any sort of Palestinian state.
Palestinian Information Minister Yasser Abed Rabbo said that "any initiative or any idea is worthless today, because what's important is the Israeli invasion."
Rabbo said it was "the responsibility of the American administration to pressure the Israelis to pull back before talking about initiatives and peace talks."
In Ramallah, the Palestinian political headquarters in the West Bank, Israeli soldiers atop armored personnel carriers flashed V-for-victory signs as dozens of tanks and armored personnel carriers rolled into the city under the cover of two helicopters.
The troops took up positions around Arafat's offices, where a bulldozer quickly began fortifying barriers at the front gate. More than 20 tanks were parked on the street that surrounds Arafat's compound Monday afternoon.
Israel forces have besieged Arafat's compound on and off since last December, and Monday's action marked the third time this month to troops have surrounded his offices, which now consist of many battered and scorched buildings that cover a full city block.
"The Israeli government, with these continuous attacks, has revealed to the whole world its real intentions," Arafat said in a statement issued by the Palestinian news agency Wafa. "Nothing can weaken our belief in our legal right to have our own independence and freedom, and all this Israeli aggression will not achieve any political results."
Arafat was inside the compound with security aides and was not harmed. The Israelis faced no real resistance as they moved into Ramallah, and have now taken over six of the eight main Palestinian cities and towns in the West Bank since launching the invasion last week.
Within an hour of moving into Ramallah and adjoining el-Bireh, Israeli soldiers announced on loudspeakers that a curfew had been imposed on the area's 200,000 residents, as in the other towns.
The army said it had taken up "strategic points" in Ramallah, was controlling access to the city, and had placed the area under curfew. Palestinians detonated explosives, slightly injuring one soldier, the army said. The streets were deserted except for Israeli jeep patrols.
"There's no doubt that with the current situation, it's hard to see how we can fight terror effectively without being in the Palestinian areas," Cabinet Secretary Gideon Saar told Israel Radio.
At least 600,000 Palestinians in the West Bank are confined to their homes by the curfews, although restrictions were temporarily lifted in two places, Nablus and Qalqiliya, so residents could shop and go to school.
The Palestinian leadership accused Israel of using the invasion as a pretext for getting rid of the Palestinian Authority and putting an Israeli military administration in its place.
"This is not a temporary step. It is a comprehensive and long-term Israeli plan that aims to destroy the future of the Palestinian people and the destiny of peace and security in the region," the statement said.
Israeli officials have denied the charge. An Israeli military administration presided over Palestinians until creation of the Palestinian Authority in 1994.
Meanwhile, Hamas renewed its threats against Israel and warned Arafat to lift the house arrest order against Yassin, the group's leader.
"We emphasize our right to continue the jihad (holy war) and resistance, and to intensify the martyrdom operations as a reaction to the policy of the occupation and the (Palestinian) authority," Hamas said in a statement.
In other developments in the West Bank, Israeli forces arrested 10 wanted Palestinians in and around Hebron, the army said. Many were known to be Hamas members, Palestinians said.
In Jenin, Israeli troops carried out house-to-house searches, arresting the head of Palestinian military intelligence, Mohammed Abu Hanana, and his bodyguard, Palestinian security officials said. Troops also found an explosives lab, along with rockets and two explosives belts ready to be used by suicide attackers. The army destroyed the lab using a controlled detonation.