The son of the former Egyptian President Mohamed Morsi has died from a heart attack, just three months after his father's sudden courtroom death.

Abdullah Morsi, who was in his 20s, fell ill while driving his car in Cairo and was rushed to a private hospital where doctors were unable to save him, the BBC reported.

Morsi, who became the country's first democratically elected president in 2012, was toppled by Sisi in a military coup the following year.

The 67-year-old's courtroom death was compared to the killing of Jamal Khashoggi at the Saudi Embassy in Istanbul by Turkey's President Recep Tayyip Erdogan, who accused Egypt of murder.

Morsi went into cardiac arrest on June 17, shortly after speaking from his glass cage at his espionage trial to warn he had 'many secrets.'

Morsi hailed from Egypt's largest Islamist group, the now outlawed Muslim Brotherhood, and was elected president in 2012 in the country's first free elections following the ouster the year before of longtime autocrat Hosni Mubarak.

The military led by the army chief, now President Sisi, overthrew Morsi in 2013 after massive protests and crushed the Brotherhood in a major crackdown, arresting Morsi and many others of the group's leaders.

In early court sessions he gave angry speeches until judges ordered him kept in a glass cage where they could turn off his audio.

Morsi's Brotherhood accused the government of 'assassinating' him through years of poor prison conditions. 

A group of British parliamentarians had warned in March 2018 that Morsi's detention conditions, particularly inadequate treatment for his diabetes and liver disease, could trigger 'premature death'.