United Nations human rights chief Michelle Bachelet on Sunday urged Egypt's appeals court to overturn mass death sentences handed down by a lower court after what she said was an "unfair trial", Reuters reports.
The former Chilean President, who took office as UN High Commissioner for Human Rights last week, criticised a law giving immunity from future prosecution to senior military officers.
An Egyptian court on Saturday delivered death sentences to 75 people, including prominent Islamist leaders Essam al-Erian and Mohamed Beltagi, over a 2013 sit-in that ended with security forces killing hundreds of protesters.
If carried out, the sentences "would represent a gross and irreversible miscarriage of justice", Bachelet said in a statement.
Egypt rejected Bachelet's comments and said they were influenced by "the terrorist Muslim Brotherhood lies", the foreign ministry said in a statement late on Sunday.
Read: Egypt adjourns Morsi's espionage trial
Defendants were denied the right to individual lawyers and to present evidence, while "the prosecution did not provide sufficient evidence to prove individual guilt", she said. "I hope that the Egyptian Court of Appeal will review this verdict and ensure that international standards of justice are respected by setting it aside," Bachelet said.
The sentencing, which included jail terms for more than 600 others, concluded a mass trial of people accused of murder and inciting violence during the pro-Muslim Brotherhood protest at Rabaa Adawiya square in Cairo.
The decision can be appealed within 60 days.
Since 2013, Egyptian courts have sentenced hundreds to death, but most sentences were appealed, and very few carried out.
Amnesty International has condemned Saturday's decision, calling the trial "disgraceful".
Read: Egypt sentences 75 to death, hundreds to jail over Rabaa sit-in
Bachelet decried the "lethal military crackdown" saying it had led to the killing of "up to 900 mostly unarmed protesters by members of the Egyptian security forces". The Government later claimed that many protesters had been armed and that some police were killed, she added.
The Rabaa square demonstration in 2013 had followed weeks of protests against the ousting of Islamist President Mohamed Mursi by the Sisi-led military.
"Despite the huge death toll, no State security personnel have ever been charged in relation to the so-called 'Rabaa massacre'," Bachelet said.
A law passed in July gives Sisi the right to name officers who are eligible for immunity from an investigation of offences alleged to have been committed while Egypt's constitution was suspended between Mursi's overthrow on July 3, 2013, and the reconvening of parliament on Jan. 10, 2016.
"Justice must apply to all – no one should be immune," Bachelet said.
"I urge the Government of Egypt to ensure that justice will be done, according to law, in relation to any individuals – including members of the state security forces – who are suspected of committing a crime."