Hundreds of supporters of Egypt's deposed president Mohamed Morsi, including the head of his Muslim Brotherhood movement, were due to stand trial on Tuesday in the same court district that handed down death sentences to another 529 of the ousted leader's backers the previous day.
The 683 co-defendants in Tuesday's trial include Brotherhood Supreme Guide Mohamed Badie, along with several of the Islamist movement's leaders.
Defence lawyers boycotted Tuesday's court session. Only 60 defendants attended the session and the rest at large.
The trials' proceedings, which take place in the southern governorate of Minya, will span until Thursday when a court decides if other rounds of hearings will take place, the same source said.
Badie was not present at the session since he stands multiple trials on an array of charges including inciting murder and belonging to a terrorist group – as the Brotherhood has become designated by authorities.
The defendants face numerous charges that include murder, disrupting public order and attacking public and private property, according to judicial sources.
The allegations are related to the violence that broke out in Minya in the aftermath of the forced dispersal of two Cairo pro-Morsi protest camps on 14 August.
Monday's sentences handed to 529 pro-Morsi defendants, arguably the largest mass death sentencing in Egypt's modern history, came after two hearings that started on Saturday.
The verdict drew a chorus of condemnation from rights groups, Washington and the European Union, with many questioning the fairness of the proceedings. Experts argue the sentences are likely to be overturned on appeal.
The exceptionally swift trial and harsh sentences highlight the escalation of a sustained crackdown on Islamists since the military's 3 July, 2013 overthrow of Morsi following mass nationwide protests against his turbulent year in power.
At least 1,400 people, mainly Islamists, have been killed in street violence since Morsi's ouster, according to rights group Amnesty International, and thousands incarcerated.
The deposed leader himself faces a number of trials on a variety of charges, including inciting the murder of opposition protesters, espionage and a jailbreak during the 2011 uprising.
Most of the Brotherhood's senior leaders are behind bars, with a number standing trial on the same charges as Morsi, some of which carry the death penalty.
Meanwhile, a rising Islamist insurgency in the border Sinai Peninsula has increasingly targeted police and army, killing more than 200 policemen and army soldiers.
The government has declared the Brotherhood a "terrorist" group, blaming it for militant violence rocking the country. The group denies any links to violence and says it is committed to peaceful politics.
