"In some instances, Saudi border guards asked migrants what limb to shoot, and then shot them at close range," the report states. "Saudi border guards also fired explosive weapons at migrants who were attempting to flee back to Yemen."
"I saw people killed in a way I have never imagined. I saw 30 killed people on the spot."
"If committed as part of a Saudi government policy to murder migrants, these killings, which appear to continue, would be a crime against humanity," HRW said.
One 14-year-old Ethiopian girl from the Oromia region said: "I saw people killed in a way I have never imagined. I saw 30 killed people on the spot."
One migrant said that out of 150 people in their group, "only seven people survived that day" after they came under heavy fire, and that "there were remains of people everywhere, scattered everywhere."
Another survivor said he was part of a group of 170 Ethiopian migrants who were attacked while trying to cross the border.
"I know 90 people were killed, because some returned to that place to pick up the dead bodies—they counted around 90 dead bodies," he said.
One Ethiopian interviewed by HRW said he went to the Saudi border to retrieve the body of a girl from his village who was killed while trying to enter the kingdom.
"Her body was piled up on top of 20 bodies," he said. "It is really impossible to count the number. It is beyond the imagination. People are going in different groups day to day. The dead bodies are there."
A 17-year-old boy said Saudi border guards "forced him and other survivors to rape two girl survivors after the guards had executed another migrant who refused to rape another survivor."
Mustafa Soufia Mohammed, a 21-year-old Ethiopian who is not in the HRW report, told the BBC he attempted to enter Saudi Arabia last July in a group of about 45 people seeking work in the wealthy kingdom when border guards opened fire on them.
"The shooting went on and on," Mohammed said. "I didn't even notice I was shot, but when I tried to get up and walk, part of my leg was not with me."
Mohammed lost one of his legs and is now back in Ethiopia.
"I went to Saudi Arabia because I wanted to improve my family's life," the father of two said, "but what I hoped for didn't materialize. Now my parents do everything for me."
Last year, a group of United Nations experts wrote to the Saudi government expressing alarm over "what appears to be a systematic pattern of large-scale, indiscriminate cross-border killings, using artillery shelling and small arms fired by Saudi security forces against migrants."
In July, the Mixed Migration Center—an independent branch of the Danish Refugee Council—said in a report that Ethiopians were being "systematically" killed by Saudi state forces.
The Saudi monarchy rejects reports of mass migrant killings by its border guards.
"Based on the limited information provided, authorities within the kingdom have discovered no information or evidence to confirm or substantiate the allegations," the government said in response to the U.N. experts' letter.
HRW refugee and migrant rights researcher Nadia Hardman said in a statement Monday that "Saudi officials are killing hundreds of migrants and asylum-seekers in this remote border area out of view of the rest of the world."
"Spending billions buying up professional golf, football clubs, and major entertainment events to improve the Saudi image should not deflect attention from these horrendous crimes," asserted Hardman, who in a separate BBC interview described "sites that sounded like killing fields."
Connor Echols of the Quincy Institute for Responsible Statecraft wrote Monday that "the accusations come at a particularly sensitive time for the Saudi monarchy, which has embarked on a massive public relations push in order to burnish a global image tarnished by alleged war crimes in Yemen and the grisly 2018 murder of Saudi journalist and Washington Post opinion writer Jamal Khashoggi."
Echols continued:
The report also raises uncomfortable questions for the Biden administration, which is considering giving "security guarantees" to Saudi Arabia in order to entice its leaders to normalize relations with Israel. Among the proposals on the table is a mutual defense treaty that would obligate U.S. troops to defend Saudi Arabia in case of attack. American officials are also mulling whether to help Riyadh develop a civilian nuclear program, a move that many experts worry could be a first step toward a Saudi nuclear weapons push.
Sarah Leah Whitson, executive director of Democracy for the Arab World Now, told Echols that U.S. backing emboldens Saudis to commit atrocities with impunity.
"Saudi Arabia feels empowered to act as recklessly, inhumanely, and unlawfully as it wants—including lobbing mortar attacks on desperate migrants seeking safety—because it knows it has U.S. support," she said.
"We can expect that its reckless belligerence will only increase with the added security of a U.S. security guarantee," Whitson added. "The Biden administration should take responsibility for its role in knowingly aiding and abetting Saudi security forces."