Israeli Prime Minister Ariel Sharon suffered a "significant stroke" on Wednesday and is under sedation and receiving breathing assistance while being treated, said a hospital official.
Deputy Prime Minister Ehud Olmert will temporarily assume Sharon's powers, Cabinet secretary Israel Maimon said.
Reports say he suffered a cerebral hemorrhage, or bleeding inside his brain. An Israeli media report says Sharon is suffering paralysis in his lower body.
The 77-year-old was taken by ambulance to Jerusalem's Hadassah Hospital. He had been staying at his ranch in Israel's southern Negev desert region ahead of routine heart surgery on Thursday.
- INDEPTH: Sharon Milestones
Israeli media reports said he was taken into the hospital on a stretcher, complaining of chest pressure or pain.
The Israeli leader is supposed to have surgery on Thursday to repair a tiny hole in his heart. Doctors called the procedure routine, saying the birth defect was discovered when he had his first stroke two-and-a-half weeks ago.
- FROM DEC. 26, 2005: Sharon to undergo routine heart surgery
- FROM DEC. 18, 2005: Ariel Sharon recovering in hospital after minor stroke
Sharon had a minor stroke on Dec. 18 and spent a couple of days in hospital. Doctors said he would not suffer any long-term effects from the stroke and ordered Sharon, who is 5'7" and weighs 260 pounds, to lose weight.
He has been taking blood-thinning medication to prevent another blood clot.
Sharon, who orchestrated September's Israeli pullout from Gaza, recently quit Likud and formed his own party, Kadima. Israel is set to hold general elections at the end of March.