Human Rights Watch has described last year's killings during the dispersal of two Cairo protest camps held by supporters of ousted president Mohamed Morsi as planned in advance and likely "a crime against humanity".
In its 188-page investigation, released Tuesday, the New York-based rights group presents evidence of Egyptian security forces using excessive force to disband the sit-in in front of Rabaa Al-Adaweya Mosque in the east Cairo district of Nasr City.
At least 817 were killed during the dispersal that day, 14 August 2013, the report said, while other estimates put the death toll at more than 1,000. Another 800 were arrested at the sit-in.
The report states that the excessive force was planned and that larger death tolls had been expected.
"In Rabaa Square, Egyptian security forces carried out one of the world's largest killing of demonstrators in a single day in recent history," said Kenneth Roth, HRW executive director.
"This wasn't merely a case of excessive force or poor training. It was a violent crackdown planned at the highest levels of the Egyptian government. Many of the same officials are still in power in Egypt, and have a lot to answer for."
Despite the high death toll, the report said, not even a single low-level police officer was held accountable – rather, bonuses were given to those who participated in the dispersals.
As a result of its findings, HRW has called for an international investigation and prosecution of those implicated. HRW further called on states to suspend military and law enforcement aid to Egypt until it adopts measures to end its serious rights violations.
HRW said it interviewed more than 200 witnesses – including protesters, doctors, local residents and independent journalists – visited each of the protest sites during or immediately after the attacks began and reviewed physical evidence, hours of video footage and statements by public officials. The group wrote to relevant Egyptian ministries soliciting the government's perspective on these events – but received no responses, it said.
Detailing the execution of the dispersal plan, the report said security forces attacked the Rabaa encampment from each five of its main entrances, using armed personnel carriers (APCs), bulldozers, ground troops and snipers.
In contrast to security forces later saying they had given demonstrators adequate time to leave before the dispersal, the report claimed there was "little to no effective warning … leaving no safe exit for nearly 12 hours" and that there was also firing on makeshift medical facilities.
The government said at the time that the protesters had been armed. However, after fully clearing the sit-in on 14 August, Interior Minister Mohamed Ibrahim announced that his forces had found 15 guns in the square.
"[That] figure, if accurate, indicates that few protesters were armed and further corroborates the extensive evidence Human Rights Watch compiled that police gunned down hundreds of unarmed protesters," the report said.
"Lethal force should be used only when strictly unavoidable to protect an imminent threat to life – a standard that was far from met in this case."
The report also presents evidence of violence from protesters, who it says threw rocks and Molotov cocktails at police when the dispersal began and, in some cases, fired on police. Forensics records showed that eight police officers died that day, the report noted.
Other violent incidents in July and August are detailed, including those outside the Republican Guard headquarters, outside a mosque in Ramses Square and the dispersal of a smaller sit-in in central Cairo.
"The legacy of the Rabaa massacre continues to cast a dark shadow over Egypt," Roth said. "Egypt will not move forward until it comes to terms with this bloody stain on its history."
In response to the HRW report, the Egyptian government issued a statement early Tuesday in which it called the findings biased and negative.
"The Egyptian government is sorry that the Human Rights Watch report deliberately didn't mention that hundreds of civilian, police and army martyrs have been killed up until now by those described in the report as [peaceful protesters]," said the statement from the State Information Service, the government's communications department.
"The report ignored that the first fallen martyr killed by a firearm during the dispersal of the Rabaa sit-in was a police officer."
The SIS statement accused the HRW report of being biased towards the "claims of ... the terrorist Muslim Brotherhood organisation".
It also said the report failed to take into account reports from the National Council for Human Rights – the government appointed rights body – and other NGOs that showed Egyptian authorities had acted in accordance with both Egyptian and international standards during the dispersal.
The government accused HRW of "breaking the law" by conducting its interviews and research in Egypt without legal permits.
On Monday, Roth and HRW Middle East and North Africa Director Middle East and North Africa Director Sarah Leah Whitson were barred entry to Egypt at Cairo International Airport.
The two had been scheduled to publicly release the Rabaa report from Cairo on Tuesday in front of journalists and diplomats. However, authorities held them at the airport and then deported them hours later, citing security reasons.
It was the first time Egyptian authorities have prevented HRW employees from entering the country.
The rights group closed its Cairo office in February, citing concerns over Egypt's deteriorating security and political situation.