The death sentences handed out by an Egyptian court against 529 supporters of the outlawed Muslim Brotherhood have sparked widespread outrage and international condemnation.
Rights groups, the United States and the European Union expressed concern and questioned the fairness of proceedings against so many defendants lasting just two days.
The largest mass sentencing in the country's history was a sharp escalation of a crackdown on the Muslim Brotherhood that the military-installed government has declared a "terrorist organisation".
Monday’s sentences in the central city of Minya were related to the death of a policeman and other violence that took place across the country since July, when the army overthrew Egypt's first freely elected president, Mohamed Morsi of the Muslim Brotherhood.
Nearly 700 other Muslim Brotherhood supporters, including Mohamed Badie, the supreme guide of the movement, are due in court on Tuesday.
Amnesty International said the death sentences were "a grotesque example of the shortcomings and the selective nature of Egypt's justice system".
The UK-based rights group said it was the "largest single batch of simultaneous death sentences we’ve seen in recent years, not just in Egypt but anywhere in the world," and called for the verdicts to be quashed.
Legal experts said the shock verdict would likely be overturned on appeal because the court had rushed the trial without following the required procedures.
Lawyers said the judge brought the case to a close after two sessions and refused to allow the defence to complete their cases.
But Egypt's army-installed interim government defended the court's handling of the case, insisting that the sentences had been handed down only "after careful study" and were subject to appeal.
Washington said it was "deeply concerned" about the death sentences.
"While appeals are possible, it simply does not seem possible that a fair review of evidence and testimony consistent with international standards could be accomplished with over 529 defendants after a two-day trial," a State Department official said.
The US partially suspended its $1.5bn in annual aid to longtime ally Egypt, much of it to the military, after last summer's crackdown on the opposition.
EU foreign policy chief Catherine Ashton urged Egyptian authorities to grant defendants "the right to a fair and timely trial" and said "capital punishment can never be justified".
Defence counsel Mohamed Tousson charged that the judge had rushed to sentencing on Monday after being angered by a lawyer's request for his recusal at Saturday's opening hearing.
"He got very angry, and adjourned the trial for sentencing," Tousson told AFP news agency. "It's a huge violation of defendants' rights."
The Muslim Brotherhood said the death sentences were yet "another indication that the corrupt judiciary is being used by the coup commanders to suppress the Egyptian revolution and install a brutal regime".
At least 1,400 people have been killed in the crackdown on Morsi's supporters and thousands more arrested, according to Amnesty International.
Of the 529 sentenced on Monday, only 153 are in custody. The rest were tried in their absence and have the right to a retrial if they turn themselves in. Another 17 defendants were acquitted.
Morsi is himself currently on trial in three different cases. He was toppled by the army after a single year in power following mass protests demanding his resignation.