Egypt 'opens trial' of acting Muslim Brotherhood leader
"The hearing was held before the State Security Court at Tora Prison" in the capital Cairo, the source said, on condition of anonymity.
The next hearing was set for January 4 "for procedural reasons", the source added.
Ezzat, 76, was arrested in late August in Cairo after seven years on the run.
He has already been handed two death sentences in absentia, as well as life imprisonment.
He was sentenced in 2015 on charges related to the assassination of military and state officials.
The trial that opened on Thursday sees Ezzat accused of overseeing the murder of soldiers and state officials, notably the 2015 assassination of former attorney general Hisham Barakat, according to the judicial source.
He also stands accused of "supervising the explosion of a vehicle in front of the National Institute for Cancer", an attack that killed 20 people in August 2019, the source said.
He is further charged with having "directed cyber militias".
Ezzat, a member of the Brotherhood since the 1960s, spent time in prison under the presidencies of both Gamal Abdel Nasser and Hosni Mubarak, and has served as the organisation's acting leader several times.
Founded in 1928, the Brotherhood established itself in the mid-20th century as the main opposition movement in Egypt, as well as in other countries in the region.
But the movement was wiped from Egypt's political landscape in 2013, after a brief one-year tenure by one of its members Mohamed Morsi, who was ousted by the army on the back of mass protests against his presidency.
Since then, Egypt has jailed thousands of members and supporters of the group and executed dozens, while others fled to countries more favourable to their ideas, such as Qatar or Turkey. Morsi himself died while on trial in June 2019.
According to rights groups, more than 800 Muslim Brotherhood supporters were killed in a single day in August 2013 during demonstrations in the capital.
Cairo blacklisted the Brotherhood as a "terrorist" organisation in 2013, but the Islamist group has consistently denied any link to violence.