Prime Minister Ariel Sharon's intracranial pressure returned to normal Friday and he was showing "significant improvement" after five hours of emergency brain surgery, hospital officials said.

Sharon, 77, underwent a brain scan after the surgery and was returned to the intensive care unit, where he remains in serious condition, said Hadassah Hospital director Dr. Shlomo Mor-Yosef.

"I can say that in comparison to previous CT scans ... there is a significant improvement in the way the brain exam looks to Hadassah's experts," Mor-Yosef said.

Sharon suffered a massive stroke with widespread bleeding in his brain Wednesday, and Friday's surgery was his third operation since then.

The premier was rushed into the operating room after doctors detected bleeding in the brain, increased cranial pressure and rising blood pressure.

Mor-Yosef said the prime minister was in "stable, but serious" condition.

Wednesday's stroke was Sharon's second since a mild one Dec. 18, and occurred the night before he was scheduled to undergo a procedure to repair a hole in his heart. That tiny hole contributed to the earlier stroke.

Shimon Peres, Israel's elder statesman and a Sharon ally, said he was "very worried."

Friday's surgery followed two operations performed after Sharon suffered a massive brain hemorrhage on Wednesday. Doctors had put him in a medically induced coma to give his body time to heal, but most outside experts said his chances for recovery were slim.

He will remain in a medically induced coma until Sunday, his doctors said.

Sharon's sons, Omri and Gilad, were camped out in a room next door to their father's at the neurological intensive care unit.

Dr. Yonathan Halevy, a senior doctor at Jerusalem's Shaarei Zedek Hospital who is not treating Sharon, said he was also worried about the Israeli leader's condition.

"The fact that the bleeding has resumed is a sign of a significant deterioration," he told Israel TV.

Outside medical experts said bleeding from the stroke may have led to interference of the drainage of the cerebral spinal fluid that bathes the brain, or he may have developed inflammation and fluid leakage within the substance of the brain.

FOX News has learned that after Sharon's massive stroke and brain hemorrhage, doctors were ready to pronounce the Israeli leader dead, but were dissuaded from doing so by family and close associates. They promised to do everything they could to save Sharon's life.

Sharon's sudden, grave illness left his ambitious peace agenda in doubt and stunned Israelis, who were grappling with the likelihood that the man who dominated politics in the regions for decades would never return to power.

"Between hope and despair," read the banner headline in the Maariv daily newspaper.

Aides to Sharon said they were working on the assumption he would not return to work.

Sharon's supporters prayed for his recovery. Sephardic Chief Rabbi Shlomo Amar advised Israelis which Psalms to read as part of their prayers for Sharon.

Rabbi Shmuel Rabinovitch of the Western Wall said he received dozens of e-mails praying for Sharon's health that he printed out and stuck in the cracks of the holy site. Callers from as far away as Venezuela and the United States asked for advice in praying for Sharon, he said.

Svetlana Kremitsky, a hospital worker who brings food to the patients in Sharon's ward, said the hospital was filled with worry.

"You can feel it in the air. We're all concerned," she said.

Sharon's deputy, Ehud Olmert, has taken the reins as acting prime minister and is trying to convey a sense of stability. Olmert has made a deliberate point of not sitting in Sharon's chair or giving the appearance of replacing him, however.

Leaders of Sharon's new Kadima Party said they would rally around Olmert and a new poll released Friday showed Kadima would still sweep March elections, even without Sharon.

Olmert spoke with Secretary of State Condoleezza Rice on Friday morning. Rice canceled a trip to Indonesia and Australia amid the uncertainty over Sharon's condition, State Department spokesman Sean McCormack said Friday.

Doctors said it would take time to determine how much damage was caused by the widespread stroke Sharon suffered Wednesday night, adding that media reports of permanent, significant damage were irresponsible.

Palestinians reacted to the fall of their longtime enemy with a mix of glee and apprehension. Some Palestinian leaders worried that Sharon's illness could derail their Jan. 25 parliamentary elections.

"We are watching with great worry at what might happen if he is harmed," said Palestinian leader Mahmoud Abbas, who called Olmert to express wishes for Sharon's recovery.

Some Palestinian children gave out sweets in the Gaza Strip at news of Sharon's illness.

Foreign leaders, who embraced Sharon following his unilateral pullout from the Gaza Strip last year, also expressed concern.

Secretary of State Condoleezza Rice praised Sharon as "a man of enormous courage," and British Foreign Secretary Jack Straw said he was praying for a miraculous recovery.

Two prominent rabbis visited Sharon's bedside Thursday on the heavily guarded seventh floor of the hospital and prayed with his family, one of the rabbis, Yitzhak Batzri, told Israel Radio. Batzri's father, leading Jewish mystic David Batzri, held Sharon's hand to direct a prayer toward him, Yitzhak Batzri said.

"He is unconscious as everyone knows and the small happiness that we have is that we saw the family is strong, the family believes, the family is praying and hoping," Yitzhak Batzri said.

Israelis were shocked by the illness of a man who was in public life for decades, first as a hero in Israel's earliest wars and later as the country's best known political hawk. Sharon led Israel's fight against the Palestinians during nearly five years of violence, and his security credentials gave him the credibility with the Israeli public to make concessions to the Palestinians.

"He was one of a kind. I don't know any other man like him," said Joseph Lapid, head of the opposition Shinui Party.

Sharon first rose to prominence as an army officer, setting up a unit that fought Palestinian infiltrators in the 1950s. He served as a commander of the Gaza region after Israel captured the territory in 1967, before entering politics and forging the hardline Likud Party.

Sharon briefly returned to the army to lead the fight against Egypt during the 1973 Mideast war.

As defense minister, Sharon directed Israel's ill-fated invasion of Lebanon in 1982 and was forced to step down by an Israeli commission of inquiry that found him indirectly responsible for a massacre of Palestinians in two refugee camps by Christian Phalangist soldiers.

Sharon re-emerged as prime minister in 2001 soon after the outbreak of new Israeli-Palestinian violence, and two years later he reversed his decades-long support for Jewish settlement and pushed through his Gaza pullout plan.

Despite the pullout, Sharon remains widely reviled in the Arab world for his tough actions against Palestinians.

Sharon fell ill Wednesday evening while he rested at his ranch in southern Israel ahead of a medical procedure scheduled for Thursday to close a small hole in his heart. Doctors rushed him to Hadassah Hospital, instead of a hospital in nearby Beersheba, because his condition did not appear dire, Sharon aides said. He suffered the bleeding stroke during the hourlong drive to Jerusalem.

A hospital director, speaking anonymously to the Haaretz daily, said Sharon should have been in the hospital the night before his heart procedure, and he called the treatment "negligent."

FOX News' Amy Kellogg and The Associated Press contributed to this report.