Egypt's Hosni Mubarak is in a coma on life support at a Cairo hospital after suffering a stroke in prison, medical and military sources have reported.

The uncertainty over the health of the ousted leader came against the backdrop of new tension in the country, with both candidates in a presidential vote claiming victory and the ruling military claiming sweeping new 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 that was confirmed by a member of Egypt's ruling military council, who spoke on condition of anonymity.

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

But earlier, state news agency MENA said Mubarak, 84, had been declared clinically dead after suffering a stroke in prison and being transferred to hospital.

"Hosni Mubarak is clinically dead," the official news agency reported.

"Medical sources told MENA his heart had stopped beating and did not respond to defibrillation."

A security source said Mubarak's wife Suzanne was visiting him in hospital, and state television said an "official statement" on his health would be released "soon," giving no further details.

Mubarak was taken to a Cairo prison on 2 June, after a court handed down a life sentence against him over his involvement in the death of protesters during the 2011 uprising that pushed him from power.

His health deteriorated after the transfer, with doctors defibrillating him twice earlier this month, and reports saying he was suffering from bouts of depression, high blood pressure and shortness of breath.

The news of his failing health came against a backdrop of renewed tension over Egypt's difficult transition, with both candidates in a key presidential vote that wrapped up on Sunday claiming victory in the poll.

The Muslim Brotherhood said their candidate Mohammed Mursi had won the run-off vote in the early hours of Monday morning, and yesterday provided what they said were certified copies of ballot tallies to bolster their claims.

But Mursi's rival Ahmed Shafiq, Mubarak's last prime minister, has also claimed a victory, with his campaign accusing the Brotherhood of issuing false figures and insisting official results scheduled tomorrow will declare him president.