RAMALLAH, West Bank — Palestinian leader Yasser Arafat, who has been ailing for more than a week, collapsed and fell briefly into unconsciousness Wednesday night at his compound, Palestinian officials said.

Doctors and senior aides were urgently summoned to the 75-year-old Arafat's half-ruined headquarters in the West Bank town of Ramallah. Palestinian officials said a three-member committee had been chosen to handle day-to-day affairs in the event that Arafat — who has always refused to designate a successor — cannot.

Though there have been scares over Arafat's health before, this is the first time any kind of panel has been named to take over in case he becomes incapacitated.

The officials, speaking on condition of anonymity, also said that all Palestinian security forces had been ordered to report for duty.

Israeli and Palestinian officials have long feared that Arafat's death or incapacitation could trigger a slide into chaos in the West Bank and Gaza Strip. Israeli media reported this year that the Israeli army had rehearsed war game scenarios of riots breaking out across the Palestinian territories on Arafat's death.

The Palestinian Authority president, under virtual house arrest by Israel in his West Bank headquarters since 2002, has been sick for more than a week with what associates have variously described as a bad case of the flu, gallbladder disease or both.

Arafat's collapse was reported by two Palestinian officials who cited a witness account and spoke on condition they not be named. Publicly, however, aides denied that the situation was critical.

"His situation is stable and not worrisome," Nabil abu Rudaineh, a senior Arafat aide, told reporters who gathered outside the battered Ramallah compound, known as the Muqata. "But he needs rest and care." Asked if Arafat was unconscious, would need surgery or had otherwise taken a turn for the worse, Azzam Ahmad, Arafat's minister of telecommunications, repeatedly responded: "Absolutely not! Absolutely not!"

Early today, Reuters quoted one official as saying Arafat joined morning prayers at his compound, though he was still very ill.

Wednesday, aides said tests, including a biopsy and blood work, had ruled out intestinal cancer as a cause of Arafat's severe recurring stomach pains. On Tuesday, reports cited a member of his medical team as saying the Palestinian leader had a large gallstone, which was painful but did not pose a serious threat to his health.

Prime Minister Ahmed Korei and his predecessor, Mahmoud Abbas, were among those who arrived at the Ramallah compound for a late-night visit Wednesday. Both men were once close to Arafat and for many years were considered his likeliest successors, but both quarreled sharply with him after becoming prime minister.

Abbas quit last year, accusing Arafat of sabotaging him, and Korei has also threatened to step down. Despite those rifts, sources said the two men, together with senior Palestine Liberation Organization official Salim Zanoun, were named to the emergency committee. Arafat approved a decree creating the panel, the sources said.

After spending about an hour in the compound, Abbas and Korei left together, in what some interpreted as a sign that Arafat was stable for the time being.

Abu Rudaineh told reporters that both Egyptian President Hosni Mubarak and Jordan's King Abdullah II had offered to send medical teams to tend to Arafat. A team of Tunisian medical specialists has been in Ramallah since last week.

Arafat's estranged wife, Suha, who lives in France with their daughter, Zahwa, was expected to arrive in Ramallah today, Palestinian officials said.

All day Wednesday, well-wishers in SUVs and air-conditioned sedans arrived in a steady stream at the compound, some waved through and others turned away. Now and then, an Israeli army jeep would make a circuit of the dusty street outside the compound's high walls.

In four decades as the standard-bearer for the Palestinian cause, Arafat's trademark has always been an air of indestructibility. He has survived guerrilla warfare, internal feuds, assassination bids and a plane crash.

For many Palestinians, even those who bitterly resent the pervasive cronyism and corruption in his government, Arafat remains a living icon of statehood hopes, the only leader they have ever known.

But he has always been an autocrat who regards any potential successor as a threat. Again and again, he groomed charismatic aides such as Mohammed Dahlan, his former security chief in Gaza, only to repudiate them when they grew too powerful or popular.