Shimon Peres, Israel's former president, has been put into an induced coma by doctors after suffering a stroke.
The 93-year-old elder statesman was stable and fully conscious before being rushed to the hospital on Tuesday, his spokeswoman Ayelet Frisch said in a statement.
Israeli TV stations later said Peres was suffering bleeding in the brain and described the stroke as serious.
"Shimon, we love you and the entire nation is wishing for your recovery," Prime Minister Benjamin Netanyahu said in a statement.
Speaking from outside the Ramat Gan hospital late on Tuesday, Chemi Peres, the former president's youngest son, said that he hoped for the best.
"We understand the concern, we understand that people are interested in his situation and we promise to keep you updated as much as we can," he said.
"I am optimistic. I am a great believer in my father. He is a unique person."
Peres had a political career spanning nearly seven decades, serving in a dozen cabinets and twice as a Labour Party prime minister.
He later served as president from 2007-2014 before leaving government.
Peres shared a Nobel Peace Prize with Israel's late Prime Minister Yitzhak Rabin and late Palestinian leader Yasser Arafat for a 1993 interim peace deal that they and their successors failed to turn into a durable treaty.
