JERUSALEM, Oct. 20 (AP)--The Israeli-Palestinian truce brokered by President Clinton collapsed in a hail of gunfire Friday, with Israeli troops killing nine Palestinians and wounding 67. Amid the worst fighting in two weeks, Israel's prime minister said he might call a timeout in peace talks.

Friday's most vicious clash came in the West Bank town of Nablus. Just moments after 4 p.m.--the deadline Israel set for a cease-fire to take hold--Tanzim militiamen belonging to Palestinian leader Yasser Arafat's Fatah movement fired on Israeli soldiers from behind olive trees and a Palestinian police checkpost.

Massive Israeli return fire--bursts instead of the usual single shots--killed four Palestinians and wounded 20 in an intense 10-minute firefight across the West Bank's main thoroughfare. A Palestinian man, his head covered with blood, was carried by his hands and legs down a rocky slope by frantic bystanders.

Such grim scenes were replayed across the West Bank. In the town of Ramallah, a 17-year-old rock-thrower who had sought refuge behind a makeshift barricade of smoldering car wrecks was shot in the head and died instantly. Israeli soldiers kept shooting as those nearby tried to pull his body away.

The violence also edged close to Jerusalem: Palestinian gunmen fired from the West Bank towns of Beit Jalla and Beit Sahour at homes in the adjacent Jewish neighborhood of Gilo on the city's southern edge. Israel responded with fire from helicopters and tank-mounted machine guns. A mortar shell shot from a tank cannon hit an open field.

The deaths brought to 113 the number of people killed in three weeks of fighting. The vast majority have been Palestinians. The day's toll of nine dead was the highest since Oct. 6.

Each side swiftly accused the other of breaking promises to Clinton, who had prodded both to work toward a cease-fire before the weekend, when Arab nations are holding a summit with the aim of unifying their positions toward Israel.

``We can now officially state that the Palestinian Authority has not fulfilled its part in the understandings,'' Israeli government spokesman Nachman Shai said.

Israeli officials said they believe Arafat encouraged the bloodshed to drum up more support for the Palestinians at the Arab summit.

Saeb Erekat, a senior Palestinian official, said Israel was never serious about observing a truce. ``The killing field there goes on,'' he said, demanding that Clinton intervene.

Erekat said he believes Israeli Prime Minister Ehud Barak has all along been looking for excuses to withdraw from peace negotiations. ``What we are witnessing is Barak's exit strategy,'' he said.

Barak announced Friday evening that if the violence persists through the Arab summit, which ends Sunday, ``we will take time out to reevaluate the peace process.'' He said the re-evaluation period would be open-ended.

``We were the ones who were prepared to consider unprecedented ideas to bring about peace. We are also those who cannot ignore what has happened in the past three weeks and say that nothing happened,'' Barak said on Israel TV.

Barak said he spoke to Clinton by phone earlier Friday and informed him of Israel's decision to call a timeout from peace talks if violence persists.

Barak has been courting Israel's hawkish opposition leader, Ariel Sharon, who has said he would not join an emergency coalition--and thus save Barak from having to call early elections--unless Israel walked away from the peace talks. Barak and Sharon held an unscheduled meeting Friday afternoon, shortly after the truce collapsed.

The unrest began after Muslim noon prayers: Thousands of worshippers emerging from mosques across the West Bank and Gaza Strip marched toward Israeli army checkpoints and began throwing stones and firebombs.

In Ramallah, about 2,000 Palestinians unleashed a barrage of rocks, and troops responded with rubber bullets. Within a few minutes, more than two dozen rioters were injured and carried on stretchers to waiting ambulances. In a brief lull, one young man adjusted his green headband--a badge of membership in an Islamic militant group--as he crouched behind one of the makeshift barricades of car wrecks.

Behind a wall and away from the line of fire, a small group prepared firebombs, stuffing sand into the bottles for a longer burn. Others carried the crates with the bottles closer to the front lines.

At some point, soldiers fired live rounds. Israel has said firebombs are life-threatening and would draw immediate live fire.