RAMALLAH, West Bank -- Israel tightened its siege on Yasser Arafat late Friday, using tanks to destroy a stairwell in his compound, digging a deep trench and running coils of barbed wire around his offices.

By late Friday night, it became apparent that Arafat was caught in Israel's tightest chokehold yet. Three loud explosions were heard. Hours earlier, the Israelis blew up three buildings in the compound.

Nabil Abu Rdeneh, an aide to Arafat, said Israeli troops fired several tank shells at the stairwell in the section where Arafat is, to prevent people from moving between the first and second floor.

One tank shell destroyed the stairs to the ground floor below Arafat's quarters, and Israeli snipers took up positions in windows facing the rooms, Abu Rdeneh said. Two more shells were fired at another section of the building, he said.

"President Arafat and those with him are danger," Abu Rdeneh said, adding that he believed the building could collapse.

With the demolition of the walkway between the two sections of his office, Arafat and a few associates, along with about 20 wanted men, were isolated in one area and separated from most of his guards in the other section, Abu Rdeneh said.

Twenty-seven guards surrendered to Israeli troops, holding up their shirts to show they weren't carrying weapons or explosives.

The White House and the European Union urged Israel to show restraint, suggesting that too harsh a reprisal for a Tel Aviv bus blast claimed by Arafat's Islamic militant rivals would upset quiet efforts to reform the Palestinian Authority and secure a truce. Six people were killed in Thursday's bus attack.

The U.N. Security Council is expected to meet at 9 a.m. Monday to discuss the latest actions. The meeting was requested by Palestinians.

Israel said troops would only withdraw after the surrender of the 20 wanted men, who include West Bank intelligence chief Tawfik Tirawi. Arafat's aides said he would not hand over anyone to the Israelis.

Isolate, not oust

Enraged by the bus attack, Israeli Prime Minister Ariel Sharon reportedly raised the idea of expelling Arafat at an emergency Cabinet meeting Thursday. Defense minister, Binyamin Ben-Eliezer, said the plan -- for now -- was to isolate, not oust the Palestinian leader.

However, TV reports said the ultimate goal of the current assault is to make Arafat seek exile voluntarily, by confining him to a tiny area and making life in the compound unbearable. Ben-Eliezer, arguing that an outright expulsion is counterproductive and would only boost Arafat's standing, proposed that plan to Sharon in the Cabinet meeting, TV's Channel Two said.

Arafat has said he would never again leave the Palestinian lands.

Israeli bulldozers also started digging a deep trench around Arafat's office building and troops later ran bared wire around the building. Those inside said they feared the building could collapse. Security guards said a bulldozer had broken a hole into the building, near an elevator shaft.

Five Palestinians died and 25 others were wounded in during Israeli military action Friday. The dead included an Arafat bodyguard shot by snipers in the Ramallah compound.

In Gaza City, Israeli forces blew up several metal workshops where the army said weapons were made. Two Palestinians were killed and nearby houses were damaged by the explosions.

Near the town of Rafah, on the Egyptian border, Israeli troops fired on stone-throwers, killing two Palestinians and wounding 25 others, hospital officials said. The clash came after two soldiers were hurt when an explosion went off near their armored personnel carrier. The army said the soldiers were trying to salvage the vehicle were they were attacked.

The Israeli strikes were triggered by Thursday's attack, in which a suicide bomber set off nail-studded explosives on a crowded bus, killing himself, five Israelis and a 19-year-old Jewish seminary student from Scotland.

The Islamic militant group Hamas claimed responsibility in a leaflet sent to the Arabic satellite TV station Al-Jazeera.

Arafat's sprawling compound was heavily damaged in Israeli raids earlier. During a major offensive in March and April, Israeli troops confined Arafat to a few rooms for 34 days.

In June, troops reoccupied Ramallah and most other West Bank towns, and Arafat has not ventured from his compound since then, even on days when a military curfew was lifted.

Arafat was in relatively good spirits Friday, those around him said. He was kept awake at night by the shooting and bulldozers toppling walls, but performed Friday prayers -- the highlight of the Muslim week -- in his office before taking an afternoon nap. Water and electricity had not been cut, unlike in earlier raids.

Palestinian Finance Minister Salam Fayad, who said he got a few hours of sleep rolled up in a blanket on the floor, said the mood around Arafat was defiant. "We are confident of our ability to overcome this crisis," he said by telephone.

Throughout the day, Arafat spoke to several European officials and Arab leaders, including Egyptian President Hosni Mubarak, Crown Prince Abdullah of Saudi Arabia and Jordan's King Abdullah. Arafat asked them to pressure Israel to lift the siege. Arab leaders told Arafat they would seek an emergency session of the U.N. Security Council to discuss a demand for an immediate Israeli withdrawal, said Abu Rdeneh.

Washington cautioned Israel to show restraint, while also urging the Palestinians to try to prevent attacks on Israeli civilians. "Israel has the right to defend itself and to deal with security, but Israel also has a need to bear in mind the consequences of action and Israel's stake in development of reforms in the Palestinian institutions," said White House spokesman Ari Fleischer.

The flare-up comes at a time when the United States, because of its showdown with Iraq, is particularly in need of Arab good will. Harsh Israeli action against Arafat could spoil that.

The army has not released a complete list of names of wanted men, but detailed allegations against four, including Tirawi, the intelligence chief, and Mahmoud Damra, head of Force 17, Arafat's elite bodyguard unit, in Ramallah.