RAMALLAH, West Bank (AP) _ The Israeli military launched a large-scale raid on the West Bank city of Ramallah early Monday, arresting dozens of Palestinians and blowing up at least one building, the army and Palestinian security officials said.

The raid comes just hours before Israeli and Palestinian peace negotiators headed to Geneva to sign an unofficial peace plan, and a day before Palestinian factions were to meet in Cairo for cease-fire talks.

More than 60 tanks, jeeps and armored personnel carriers entered Ramallah after midnight, carrying out house- to-house searches across the city, Palestinian security officials said.

Palestinian witnesses said dozens of people were arrested, including a Hamas leader, Ghassan Abassi. Israeli military officials confirmed ``a number'' of arrests, and said they had uncovered an explosives laboratory, which the army had destroyed.

Palestinian witnesses said the army had destroyed an old house and an Internet cafe.

The army said the raid _ carried out by commandos, tanks and the Shin Bet security service _ targeted the Hamas infrastructure in the Ramallah area, which it says is behind attacks that have killed more than 60 Israelis in the last three years of fighting.

Palestinian leader Yasser Arafat has been holed up in his Ramallah headquarters for nearly two years, and Israel has threatened to expel him in the past. But despite its scope, the army stressed the raid was ``nothing unusual.''

An Israeli official, speaking on condition of anonymity, denied the raid was timed to coincide with the signing of the Geneva Accord, which the government opposes and Prime Minister Ariel Sharon has called subversive. The official said the raid was part of Israel's ``ongoing war on terrorism and not contingent on anything else.''

At Israel's Ben Gurion Airport, dozens of Israeli and Palestinian politicians, local celebrities and journalists gathered to board a Swiss charter to Geneva later Monday.

The delegates will be signing the so-called Geneva Accords, an unofficial peace plan worked out during two years of secret negotiations between Israeli opposition figures and Palestinians.

Former Israeli Justice Minister Yossi Beilin, who initiated the negotiations, said he hopes the agreement will galvanize public opinion to support the moves laid out in the plan.

``The accomplishment will be once more and more people believe we have a real plan,'' Beilin said.

The unofficial treaty proposes borders between Israel and a future Palestinian state close to Israel's borders before the 1967 Mideast war, giving the Palestinians almost all of the West Bank and Gaza Strip and part of Jerusalem.

It calls for the removal of most Israeli settlements there and largely sidesteps the so-called ``right of return'' for Palestinians who fled or were driven out during the 1948-49 war that followed Israel's creation and their descendants. It also divides sovereignty in Jerusalem.

The ceremony is to be attended by former President Carter and other winners of the Nobel Peace Prize.

Also attending Monday will be the foreign minister of Qatar and envoys from Oman and Bahrain, all Arab states that have no formal relations with Israel, organizers said. Envoys from Morocco and Egypt will also participate, along with a Saudi businessman with links to the government.

Also Monday the army blew up a house in the West Bank city of Hebron, Palestinian witnesses said. The three-story building belonged to a militant from Hamas killed by Israel in September, the witnesses said. The army had no comment.