Israel prepared Wednesday to lock down for Yom Kippur (search), the holiest day of the Jewish calendar, when borders close, streets empty of traffic and Jews fast, pray and ask for forgiveness.

In a sweep through West Bank (search) towns before the holy day, Israeli forces arrested six Palestinians, including a teenage boy allegedly coerced by militants into becoming a suicide bomber and a senior Hamas fugitive who was on the run for eight years, the army said.

In another arrest in the Hebron-area town of Dahariya (search), troops brought a fugitive's mother to call on him to surrender. When he came out of his hideout, he was forced to strip to show he had not strapped explosives to his body.

In another development, Palestinian Prime Minister Ahmed Qureia said the official investigation into the death of Yasser Arafat has failed to determine what killed the longtime Palestinian leader.

Arafat died in a French hospital on Nov. 11, 2004, after a two-week illness that saw a sudden rapid decline in his health, and the cause of death has remained a mystery. His wife, Suha, refused an autopsy.

"French and Palestinian doctors who treated the martyred brother found that medicine could not find the disease which infected Arafat, neither viruses, nor germs, nor AIDS, nor bacteria," Qureia said.

Inside Israel, security forces were on high alert for the holiday. Armed guards were to be posted at synagogues and police said extra officers would be on duty at the Western Wall, Judaism's holiest shrine, where thousands were expected to gather in prayer at midnight.

The 25-hour fast of the Day of Atonement begins at sunset and ends an hour after sundown Thursday.

According to a poll in the Yediot Ahronot daily, 70 percent of Israeli Jews said they intended to observe the fast, with residents of Jerusalem, the center of Jewish spiritual life, way above the national average at 89 percent. The paper did not say how many people were polled or what the margin of error was.

Newspapers and TV programs offered tips for the fast, advising heavy coffee drinkers to start gradually cutting down at least three days ahead. During the holiday, no food or drink is taken and the observant may not perform any physical labor, use electricity, answer the phone or operate any kind of machinery.

The ban on drinking water hits especially hard in Israel where daytime temperatures throughout the country Thursday are forecast to top 86.

From early afternoon Wednesday all public transport will cease and airports will shut down. Border points to Egypt and Jordan and crossings into the West Bank will also close.

In most Jewish neighborhoods, even the nonreligious do not drive. Israeli radio and TV channels go off the air, while shops, restaurants, cafes, cinemas and all places of entertainment shut down.

In the West Bank security sweep, the Palestinian teen whom the Israeli army said it arrested told his interrogators that militants from the Al Aqsa Martyrs' Brigades — a militant group with ties to Palestinian leader Mahmoud Abbas' Fatah movement — pressured him to carry out a suicide bombing after he quarreled with his father.

The teenager said the militants threatened to kill him and distribute a statement claiming he was a collaborator with Israel if he did not carry out their orders, the army said. It was not immediately clear how the attack was thwarted. The boy, who was identified as being 14, would have been one of the youngest suicide bombers during five years of conflict.

Jamal Tirawi, an Al Aqsa commander who allegedly recruited the boy, disputed the Israeli account.

Tirawi said the boy, whom he identified as Salah al Jitan, is 17 and came to his group volunteering to carry out an attack. Al Aqsa refused the request because the boy is the only son in his family, Tirawi said.

"The Israelis are liars," he said.

In the second arrest — in Dahariya, a town southwest of Hebron, a gunbattle erupted when troops called on Hamas fugitive Haitham Battat to surrender.

Battat's mother was brought in to call for him to surrender, telling him through a loudspeaker she loved him. Five minutes later, the fugitive left the house with his hands up. Battat was wanted in connection with a suicide bombing in Beersheba in May.