The Islamist leader, who was overthrown in 2013 after a year of divisive rule and later charged with espionage, was buried at a cemetery in eastern Cairo's Medinat Nasr, one of his lawyers said.
Abdel Moneim Abdel Maksoud said family members had washed Morsi's body and prayed the last rites early Tuesday morning at the Leeman Tora Hospital.
That lies near the prison where Egypt's first civilian president, a prominent Muslim Brotherhood member, had been held for 6 years in solitary confinement and deteriorating health.
The prosecutor general's office said the 67-year-old leader had collapsed and "died as he attended a hearing" in a retrial hearing Monday, June 17, over alleged collaboration with foreign powers and militant groups.
Abdel Maksoud told Agence France-Presse (AFP) only around 10 family members and close Morsi confidants were present, including himself.
An AFP reporter saw a handful of mourners entering the cemetery complex, accompanied by police officers, but journalists were prevented from entering the site.
The graveyard is in the same suburb as the largest massacre in Egypt's modern history, the August 2013 crackdown on an Islamist sit-in at Rabaa Square, weeks after Morsi's ouster by the military.
Over 800 people were killed in a single day as security forces moved against protesters calling for Morsi's reinstatement.
The attorney general's office said Morsi, who appeared "animated," had addressed the court Monday for 5 minutes before falling to the ground inside the defendants' cage.
Another of Morsi's lawyers, Osama El Helw, said other defendants had started banging loudly on the glass, "screaming loudly that Morsi had died".
The attorney general said he had been "transported immediately to the hospital," where medics pronounced him dead, a version of events confirmed by a judicial source.
'Killing him slowly'
Since Morsi's overthrow on July 3, 2013, his former defense minister, now President Abdel Fattah al-Sisi, has waged an ongoing crackdown that has seen thousands of Muslim Brotherhood supporters jailed and hundreds facing death sentences.
Rights groups have called for an independent probe into Morsi's detention conditions and death.
The Brotherhood's political wing – the Freedom and Justice Party – accused Egyptian authorities of "deliberately killing him slowly" in solitary confinement.
"They withheld medication and gave him disgusting food," it said in a statement. "They did not grant him the most basic human rights."
The Egyptian government has not officially commented on his death, but private television channels slammed the Brotherhood as a "terrorist group" and played a looping tagline: "The Brothers are liars".
His death barely rated a mention in local press, which referred to him by his full name but not his position as former president.
Morsi last saw his family in September 2018. A month later, one of his sons, Abdallah, was arrested.
Abdel Maksoud was the last member of his defense team to see him, in November 2017.
Rights group Amnesty International urged Egyptian authorities to open "an impartial, thorough and transparent investigation" into his death.
Human Rights Watch echoed that demand, saying Morsi had suffered years of "insufficient access to medical care".
"The United Nations Human Rights Council...should establish an investigation into ongoing gross violations of human rights in Egypt, including widespread ill-treatment in prisons and Morsi's death," it said.
A group of British parliamentarians in March 2018 warned that his detention conditions had not met international standards and could lead to his "premature death". Other Brotherhood leaders have also died in custody.
Allies such as Qatar and Turkey paid tribute to Morsi, while Iran's Foreign Ministry called his death "sad and unfortunate".
Internationally he received some support, but in his homeland, Morsi has a chequered legacy.
He spent just one turbulent year in office after the 2011 uprising, before being toppled by the military after millions took to the streets demanding his resignation.
He has been in prison since his ouster, on trial on charges including for spying for Iran, Qatar and militant groups such as Hamas.
Morsi was also accused of plotting terrorist acts.
He was sentenced to death in May 2015 for his role in jailbreaks during the uprising that ousted his predecessor, longtime autocrat Hosni Mubarak.
Morsi's turbulent rule was marked by widening schisms in Egyptian society, a crippling economic crisis and often-deadly opposition protests.
His death comes days before Egypt hosts the Africa Cup of Nations football tournament, starting Friday, June 21.
Authorities have been on high alert, announcing on Facebook Monday that thousands of forces would be deployed to secure venues. – Rappler.com