EGYPT'S ousted president, Hosni Mubarak, was in a coma on Wednesday and on life support at a Cairo hospital, sources said, as tension spiked about who will succeed him in power and moves by the military to extend its authority.

The uncertainty over the health of the elderly leader comes amid new political upheaval, with both candidates in a presidential vote claiming victory and the ruling Supreme Council of the Armed Forces granting itself sweeping powers.

Mubarak "is not clinically dead", a medical source said.

"He is in a coma and the doctors are trying to revive him.

''He has been placed on an artificial respirator," the source added, in an account confirmed by a member of the ruling military council, who refused to be named.

Egypt's state television carried a ticker item saying Mubarak was in "a coma and is not clinically dead".

State news agency Mena had earlier said the ousted strongman, 84, had been declared clinically dead after suffering a stroke in prison and being transferred to hospital.

"Hosni Mubarak is clinically dead," the report said. "Medical sources told Mena his heart had stopped beating and did not respond to defibrillation."

News of Mubarak's failing health came as Egypt wrapped up a presidential election runoff and faced "the most critical 48 hours in its history", said the state-owned daily al-Ahram.

The Muslim Brotherhood said in the early hours of Monday morning that its candidate, Mohamed Morsi, had won the runoff, and on Tuesday provided what it said were certified copies of ballot tallies to bolster its claims.

But Morsi's rival, Ahmed Shafiq, Mubarak's last prime minister, has also claimed victory. His campaign has accused the brotherhood of issuing false figures and insists that the official results due out today will declare him president.