Toppled president Hosni Mubarak has been pronounced clinically dead upon his arrival at a military hospital in the upscale neighbourhood of Maadi, according to Egyptian state news agency MENA.
Medical sources told MENA that Mubarak's heart stopped after efforts to resuscitate him failed.
However, Mubarak's lawyer Farid El-Deeb told Al-Hayat television channel that he is still alive. Efforts to revive him are beginning to have some effect, he added.
Ahram Online's correspondent overlooking Tahrir Square reports fireworks and cheering after news began trickling in of the imprisoned president's apparent death. Demonstrators began playing the national anthem over loudspeakers. The majority of the gathered crowd are Muslim Brotherhood supporters, with other groups having largely pulled out of the flashpoint square.
Mubarak was transferred to Maadi's military hospital amid tight security measures. Media personnel were denied entry to the hospital, according to Al-Ahram's Arabic news portal.
Earlier the 84-year-old former president suffered a stroke, but paramedics at the Tora Prison hospital resuscitated him with electric shocks.
Mubarak was incarcerated in Tora Prison after being given a life sentence early this month for failing to stop the killing of peaceful protesters. For months during his trial, he was held captive at the International Medical Centre, a military hospital on the Cairo-Ismailia road.
It is understood that Mubarak is suffering from cancer and heart problems. During his stay at the Medical Centre, it was reported on quite a few occasions that his heart had stopped and had to be restarted by doctors.
Revolutionary forces called for Mubarak's incarceration in Tora Prison before the verdict, to join the rest of the defendants from the former regime who were kept at the facility during their trials.
The ousted president's condition was occasionally cited as a reason to keep him away from Tora, but after being sentenced to life imprisonment, he was transferred to the notorious facility, reportedly while shouting and ranting.