Egypt's Hosni Mubarak was "clinically dead" Tuesday after suffering a stroke, the state news agency reported, as a medical source said the ex-dictator was in a coma and had been put on a respirator.
On Tuesday evening, Egyptian state news agency MENA said the ousted leader had been pronounced clinically dead at a hospital he was transferred to following a stroke in prison.
"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."
The report was carried on Egyptian state television, which ran archive footage of the former leader, with a news presenter saying "I want to affirm that the official news agency of the country, MENA, has announced it."
But a medical source told AFP that Mubarak was "in a coma and the doctors are trying to revive him."
"He has been placed on an artificial respirator," the source said.
The uncertainty surrounding his condition threatened to add new tension to the already fraught atmosphere in Egypt, and came as over 15,000 protesters crowded into Tahrir Square to protest an apparent bid by the military to grab power.
At the same time, Egyptians are waiting to hear who won the country's first post-Mubarak presidential election, with both the Muslim Brotherhood's Mohammed Mursi and ex-premier Ahmed Shafiq claiming victory in the race.
Mubarak, 84, was sentenced to life in prison on June 2 over the deaths of protesters during the uprising that ousted him.
Mursi had promised to retry him and his security chiefs, who were mostly acquitted in the same trial, if he gets Egypt's top job. The new president is expected to take office at the end of the month.
As the counting began after the end of voting on Sunday, Egypt's ruling military council issued a constitutional declaration claiming legislative power after a court ordered parliament's dissolution.
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"The dissolution of the parliament is null and void, the military council must leave and now legitimacy lies with the people who elected Mursi," said Abdel Basset Mohieddine, a Brotherhood supporter at the protest.
A confirmed win for Mursi would mark the first time the Islamists have taken the presidency of the Arab world's most populous nation, and there were jubilant scenes at his headquarters after his campaign projected victory.
Mursi has pledged to work "hand-in-hand with all Egyptians for a better future, freedom, democracy, development and peace."
Shafiq campaign spokesman Ahmed Sarhan meanwhile told reporters he was "certain that the next president of Egypt is General Shafiq," saying the former prime minister had secured 51.5 percent of the vote.
No matter who emerges as the winner, the country faces the prospect of a showdown between the Brotherhood and the ruling military.
The Brotherhood insists the parliament still has the power to legislate and said Monday it would take part in "all popular activities against the constitutional coup and the dissolution of parliament, beginning on Tuesday."
The ruling military body has introduced de facto martial law, given itself control of the legislature and state budget and also granted itself veto power on a new constitution.
The moves have sparked expression of concern from world powers, with Washington and Paris calling on the military to stick to a schedule of handing control to a civilian government.
A delegation from the Carter Centre that observed the presidential vote also expressed concern, saying the constitutional declaration and other moves by the military called "into question the meaning and purpose of the elections."
Rights group Amnesty International warned in a statement that the moves put "the country on the path to further human rights violations."
But the military has sought to quiet fears over the declaration, insisting it will transfer power to the new president on schedule by the end of this month, and pledging the new leader would enjoy full powers.
"The president of the republic will be vested with all the powers of the president of the republic," a ruling SCAF General Mohammed al-Assar told reporters.