JERUSALEM -- Israeli Prime Minister Ariel Sharon suffered a "significant" stroke last night and underwent lengthy surgery to drain blood from his brain, a hospital official said.
Doctors stopped the bleeding in an operation that lasted more than six hours this morning, but he was sent back to the operating room when a CT scan revealed that he required more treatment, said Dr. Shlomo Mor-Yosef, director general of Hadassah-Ein Kerem hospital in Jerusalem.
Mor-Yosef called Sharon's condition "serious," but did not comment on his chances of survival or recovery. The doctor said he expected several more hours of surgery. The prime minister remained on a respirator, he said.
Sharon, 77, suffered a significant stroke and a cerebral hemorrhage that involved "massive bleeding," Mor-Yosef said.
The prime minister's powers as prime minister were transferred last night to Deputy Prime Minister Ehud Olmert.
On Israeli television newscasts, medical commentators said that Sharon, given his age and health, has a slim chance of recovering fully or resuming his duties.
On Dec. 18, Sharon suffered what was characterized as a "mild" stroke. He had been scheduled to undergo surgery today to close a small hole in his heart that physicians found while treating him for the first stroke.
Sharon was rushed by ambulance from his ranch in the Negev desert to the hospital after he complained last night of feeling unwell. He was apparently conscious as the trip to Jerusalem began.
"Apparently, when he went back to his farm this evening he felt slight pains in the chest and some weakness, and, in the presence of his doctor and upon his advice, he said he should be taken to the hospital," Raanan Gissin, Sharon's spokesman, told CNN.
Israel is preparing for elections in March. If Sharon, who has served as prime minister since 2001, were to drop out of the race, there would be no clear leading candidate to succeed him.
In November, Sharon reshaped Israel's politics by breaking away from the right-wing Likud, the party he helped create three decades ago, to form the centrist party Kadima (Forward).
Sharon's new party, pledging to define Israel's borders and achieve peace with the Palestinians, has held a significant lead over rival parties in public opinion polls.
A poll released yesterday found Kadima winning 42 of parliament's 120 seats to 19 for the Labor Party, led by the fiery union leader Amir Peretz, and 14 for Likud, led by former Prime Minister Benjamin Netanyahu.
The new party's popularity has been built around Sharon. Obsessed with Israel's security, he earned a loyal following as an uncompromising military leader and then as a tough-minded political leader during the Palestinian uprisings and attacks by Palestinian militants.
Sharon surprised many of his supporters and many Palestinians last year by withdrawing Jewish settlers and Israeli soldiers from the Gaza Strip, turning his back on his long commitment to constructing settlements.
Although the majority of Israelis supported his bold move as a way to renew peace negotiations, Sharon was condemned by members of Likud, which prompted him to strike out on his own in this year's election campaign.
Sharon's long career as a soldier and politician appeared to be drawing to a close last night, Israeli political commentators said.
Israeli journalist Aluf Benn, in an analysis article on the Web site of the daily newspaper Haaretz, said it would be difficult for Sharon to return to his job.
"Even if he does recover, he will have a very hard time convincing the public of his ability to serve four more years after undergoing two strokes in two and a half weeks," Benn wrote. "One can cautiously say that it appears that the era in which Sharon stood at Israel's helm came to a tragic end on Wednesday."
With no clear successor in Sharon's new party, it was uncertain who might emerge as his replacement for the elections and whether voters would shift to Labor or Likud.
Many of Israel's top politicians have risked their political careers by breaking ranks with their parties to join Sharon's new one.
Sharon, who is 5 feet 7 inches tall and weighs about 255 pounds, is famous for his appetite and weakness for fatty foods. Despite his weight and age, Sharon was considered to be in remarkably good health, with normal blood pressure and cholesterol levels, Sharon's doctors said at a news conference last month after his first stroke.
Sharon's doctors did ask the prime minister to rest and lose weight. But mindful of the role his health would play in the political campaign, Sharon soon rushed back to work, although with a slightly lighter schedule.
Before complaining of not feeling well yesterday, Sharon had a busy day, attending a security meeting at the Lebanese border and making an appearance at a ceremony for an Israeli bank.