Former Prime Minister Ariel Sharon's health deteriorated sharply Thursday and he was in "grave condition" with his family by his bedside, the hospital treating him announced.
The Sheba Medical Center called his condition "grave" but gave no further details.
Sharon, one of Israel's most controversial and iconic figures, suffered the stroke at the height of his political power.
Sharon's career stretched across most of Israel's 65-year history.
As one of Israel's most famous generals, he was known for bold tactics and an occasional refusal to obey orders. As a politician, he became known as "the bulldozer" — contemptuous of his critics while also capable of getting things done.
He engineered Israel's 1982 invasion of Lebanon, and lost his job as defence minister after an Israeli-allied Christian militia killed hundreds of Palestinians at refugee camps in west Beirut, sparking international outrage.
Sharon managed to slowly rehabilitate his political career. For years, he was a driving force in the movement to build settlements in the West Bank and Gaza Strip, captured areas claimed by the Palestinians for a future state.
First elected prime minister in 2001, he led a tough crackdown against a Palestinian uprising, a bout of violence in which more than 3,000 Palestinians and 1,000 Israelis were killed. He remains reviled in much of the Arab world.
But in a dramatic about-face, Sharon led Israel's withdrawal from Gaza in 2005, uprooting all soldiers and settlers from the seaside strip after a 38-year military occupation.
The Gaza withdrawal led Sharon to break away from the hard-line Likud Party and form the centrist Kadima Party. His new party was cruising toward victory in 2006 parliamentary elections when he suffered his stroke.