Human Rights Watch says killings were planned at highest levels of government and calls for senior leaders to be probed.

A new report has alleged that the Egyptian security forces’ killings of at least 1,000 protesters at the Rabaa al-Adawiya Square sit-in last year in Cairo “most likely amount to crimes against humanity”.

The 195-page Human Rights Watch (HRW) report released on Tuesday found that Egyptian security forces “gunned down hundreds of unarmed protesters” when they moved in to disperse the sit-in on August 14.

The killings were “part of a policy to use lethal force against largely unarmed protesters on political grounds,” HRW found, and resulted in “one of the world’s largest killings of demonstrators in a single day in recent history”.

HRW said that over a dozen senior Egyptian leaders should be investigated for their parts in the protesters’ deaths, including Interior Minister Mohamed Ibrahim and current President Abdel Fattah el-Sisi, who was defence minister at the time.

“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,” said Kenneth Roth, HRW’s executive director, in a statement.

Roth was denied entry into Egypt on Monday, along with another senior staff member, after being held at Cairo’s international airport for 12 hours. They were on their way to Egypt to release the report.

Badr Abdel Atty, the Egyptian ministry of foreign affairs spokesperson, told Al Jazeera on Monday that the government would not comment on the report until it was officially released.

Omar Shafik, a fellow at HRW, told Al Jazeera that the group sent the full text of the report to several Egyptian ministries ahead of publication, but that the government did not respond to their requests for comment. “We didn’t receive responses to any of our queries,” Shafik said.

In a statement after the killings, however, Egypt’s state information service (SIS) said that efforts to peacefully disperse the rally were “rejected by leaders of the Muslim Brotherhood”.

“The Ministry of Interior used loudspeakers, appealed to those who were in the two sit-ins to exit, not to use women, elders and children as a human shield, they were allowed to leave and provided with safe exit passages that had been already declared,” the SIS said.

International inquiry

Tens of thousands of Egyptians began a sit-in near the Rabaa al-Adawiya mosque, in Cairo’s Nasr City district, following the military’s removal of President Mohamed Morsi on July 3 last year after major protests against his rule.

The dispersal of another sit-in, at al-Nahda Square in Giza, reportedly killed at least 87 protesters.

While initial reports on the death count at Rabaa on August 14 varied, the HRW report found that at least 1,000 protesters were likely killed during the eviction: the group confirmed 817 deaths at the Rabaa sit-in, but found reasonable evidence that an additional 246 people were also killed.

“It was raining bullets. I smelled the gas and immediately saw people being hit and falling down around me. I have no idea how many people were hit. We didn’t hear any warnings, nothing. It was like hell,” a protester later told HRW.

The Egyptian government-appointed National Council for Human Rights (NCHR) reported in March that the violence at Rabaa began after armed protesters at Rabaa shot and killed a policeman. The country’s interior ministry estimated that 43 security forces were killed that day.

But based on interviews with more than 200 witnesses, the HRW report stated that only a few protesters were armed at Rabaa; they fired on security forces in “at least a few instances”, and threw rocks and Molotov cocktails only after the break-up of the protest began.

HRW said that Egyptian security forces, meanwhile, fired on makeshift medical facilities, and “positioned snipers to target whoever sought to enter or exit” the Rabaa hospital.

The New York-based group said it would ask the United Nations Human Rights Council to establish an international commission of inquiry.

It has also called on foreign governments to cut military assistance to Egypt, “in light of the ongoing abuses and severe political repression… and the government’s failure to investigate, much less prosecute those implicated in, the mass killings of protesters”.