Prominent activist Alaa Abdel-Fattah was sentenced in absentia to 15 years in prison by an Egyptian criminal court on charges including attacking a police officer and illegally protesting, a judicial source told Ahram Online.
Abdel-Fattah, a symbol of the 2011 uprising that toppled autocrat Hosni Mubarak, is also convicted in the same trial of rioting and disturbing public order.
Twenty-four other co-defendants facing the same charges were also handed 15 years in jail.
The charges faced by Abdel-Fattah and the co-defendants stem from a Cairo protest in November of last year against provisions in a new constitution that allow civilians to be tried in military courts, which authorities said was in breach of a law banning all but police-sanctioned protests.
Abdel-Fattah was arrested over the allegations in November and detained but was released on bail late in March.
Mona Seif, Abdel-Fattah's sister and founder of the No to Military Trials group, said via Twitter that her brother, along with two other co-defendants, was waiting at the courthouse for permission to attend the session, but was denied entry.
Once the sentence was pronounced, the three were arrested at the courthouse for transfer to prison, Ahram Online's reporter at the court said.
The convicts were additionally fined LE100,000 each and will be placed under five-year police surveillance after their release upon completion of the jail term.
Abdel-Fattah and the two other convicts arrested at the court are expected to be granted a retrial.
Under Egyptian law, a retrial must be granted to defendants convicted in absentia once they are taken into custody. The sentence of a retrial can be appealed.
Defence lawyers have criticised the ruling and complained of irregularities.
"The judge has violated criminal law procedures and did not allow the lawyers to present their full defence," Ahmed Ezzat, a member of the defence team told Ahram Online, labelling the ruling as "politicised" and "vindictive".
"[The ruling] is mainly meant to exact revenge from Alaa and the others because they asked for a recusal of the bench in the case," said Ezzat, also a legal advisor in the Association for Freedom of Thought and Expression.
Abdel-Fattah was fined last month for demanding the recusal of the judge whom he accused of involvement in ballot-rigging under former president Hosni Mubarak.
The sentence came only days after former army chief Abdel-Fattah El-Sisi -- who led the ouster of Islamist president Mohamed Morsi amid mass protests against the latter's rule -- was sworn in as president.
Since Morsi's removal last July, authorities have launched a stiff crackdown on his Muslim Brotherhood movement and other Islamist sympathisers. Several pro-democracy and secular youth activists have also been rounded up in recent months for breaching the new protest law.
The law raised alarm over freedoms in Egypt and the state's tolerance of political dissent. It was condemned by local and international rights groups as draconian and heavily restrictive.