Global rights groups seek investigation into the killings of at least 900 protesters in 2013 by security forces in Cairo's Rabaa al Adawiya square, where demonstrators had rallied against the ouster of democratically-elected president Mohamed Morsi.
Global rights groups have slammed Egyptian authorities for failing to prosecute members of the security forces over a bloody 2013 crackdown on protesters that left hundreds dead.
Five years ago on August 14, 2013, security forces moved in to disperse a sprawling protest camp in Cairo's Rabaa al Adawiya square, where demonstrators had rallied against the ouster of democratically-elected president Mohamed Morsi a month earlier.
Amnesty International says at least 900 protesters were killed by security forces, marking "a horrific turning point for human rights in Egypt".
Since then hundreds of protesters, including leaders of Morsi's Muslim Brotherhood, have been convicted at mass trials.
But not one member of the security forces has been prosecuted for the deaths of protesters.
The lack of prosecutions has "contributed to an environment in which the security forces feel empowered to violate human rights with absolute impunity," said Najia Bounaim, Amnesty's North Africa campaigns director.
Egyptian officials have blamed protest leaders for the 2013 bloodshed, pointing to the presence of armed gunmen at the sit-in and the deaths of several police officers.
'Largest mass killings in Egypt's modern history'
President Abdel Fattah el Sisi last month approved a law giving senior military officers immunity from prosecution tied to the unrest that followed Morsi's ouster.
On the eve of the anniversary, Human Rights Watch (HRW) slammed Egyptian authorities for trying to "insulate those responsible for these crimes from justice".
"The response from Egypt's allies to the crimes at Rabaa and to the lack of justice for the victims has been complete silence," Sarah Leah Whitson, HRW Middle East director, said in a statement.
The US-based rights group said the protest crackdown was "the largest mass killings in Egypt's modern history", leaving at least 817 demonstrators dead.
"Without justice, Rabaa remains an open wound. Those responsible for the mass killings of protesters shouldn't count on being able to shield themselves from accountability forever," Whitson said on Monday.
'Mass show trial'
In late July an Egyptian court sentenced to death 75 people over the 2013 unrest, as part of proceedings involving 700 defendants which Amnesty described as a "mass show trial".
Among those still awaiting a verdict are prominent photojournalist Mahmud Abu Zeid, widely known as Shawkan, who in May received UNESCO's Press Freedom Prize.
Sisi's crackdown on dissent
The dispersal of the protest camp was followed by several months of deadly clashes with police in which hundreds more people were killed.
The Muslim Brotherhood was designated a terrorist organisation in Egypt in December 2013 and banned.
Former armed forces chief Sisi won the presidency in 2014 after leading the ouster of Morsi following mass protests against his rule.
Sisi won re-election with 97 percent at a vote in March against a single opponent widely seen as a token challenger, with critics saying the president had carried out a widespread crackdown on dissent.