Mohammed Morsi, Egypt's first democratically-elected president who was ousted by the military in 2013, died Monday after collapsing in court.
Egypt's public broadcaster said the 67-year-old former president was attending a session in his trial on espionage charges when he blacked out and then died.
"He was speaking before the judge for 20 minutes then became very animated and fainted. He was quickly rushed to the hospital where he later died," a judicial source told AFP.
Egypt's public prosecutor said Morsi was pronounced dead in hospital at 4:50pm local time. He said the medical report showed no apparent sign of recent injuries.
The former leader was buried in a solemn ceremony attended by his family in Cairo’s western district of Nasr City early on Tuesday, one of his lawyers, Abdul-Moneim Abdel-Maqsoud, told the AP.
Morsi, who hailed from Egypt's largest Islamist group, the now outlawed Muslim Brotherhood, was elected president in 2012 in the country's first free elections following the ouster the year before of longtime leader Hosni Mubarak.
His turbulent rule was marked by deep divisions in Egyptian society, a crippling economic crisis and often-deadly opposition protests.
The military ousted him in 2013 after massive protests and crushed the Brotherhood in a deadly crackdown, arresting its leaders and sentencing scores to death.
The years following Morsi's overthrow have seen a surge in bombings and shootings targeting security forces, particularly in the restive northern Sinai Peninsula, a stronghold of the Islamic State group.
Turkish President Recep Tayyip Erdogan, who had forged close ties with Morsi, paid tribute to the former president, calling him a "martyr."
"May Allah rest our Morsi brother, our martyr's soul in peace," said the Turkish president, later blaming Egypt's "tyrants" for his death.
Morsi's death 'predictable'
The Islamist leader had been in prison since his ouster, accused of spying for Iran, Qatar and militant groups such as Hamas in the Gaza Strip. He was also accused of plotting terror acts.
His family said he suffered from ill health due to harsh conditions, including years of solitary confinement.
Sarah Leah Whitson, Middle East director with the Human Rights Watch, tweeted that Morsi's death was "terrible but entirely predictable" given the government "failure to allow him adequate medical care, much less family visits."
The Muslim Brotherhood has described Morsi's death as a "full-fledged murder" and called on Egyptians to gather for a mass funeral.
In a strongly worded statement, Amnesty International on Monday called on Egyptian authorities to open a probe into Morsi's death.
"The Egyptian authorities must immediately order an impartial, thorough and transparent investigation into the circumstances of his death, as well as his detention conditions and his ability to access medical care," the rights group said.
(FRANCE 24 with AP, AFP)