Egypt's only freely elected president, the Islamist Mohamed Morsi, who was deposed in a 2013 military-backed coup d'etat, reportedly died on Monday during a court session, the nation's state television report.
There was no other confirmation that the 67-year-old US-educated civil engineer and political leader of the Muslim Brotherhood had died. He was on trial facing espionage charges when he reportedly collapsed.
“The body has been transferred to a hospital and necessary procedures are underway,” Nile News television said.
Born in Egyt's Nile Delta, Morsi had been imprisoned during the reign of Hosni Mubarak, but escaped during Egypt's 2011 uprising, emerging as a leading opposition figure.
He narrowly defeated a candidate supported by the military in 2012 elections, but then was felled and imprisoned in a 2013 popular uprising that led to a military takeover by Abdel-Fattah el-Sisi, Egypt's current president.
He has been held inside the notorious Scorpion section of Cairo's maximum security Tora prison, along with other Muslim Brotherhood leaders.
A report last year by a UK-based advocacy group concluded that Morsi's health was deteriorating in prison and that "failure to provide him with adequate medical treatment could lead to his premature death," describing the conditions he was being held in detention as potentially "torture."
Morsi's death during his custody in an Egyptian prison will likely anger Muslim Brotherhood supporters throughout the Middle East. The organisation is the oldest Islamist political organisation in the world.