The allegations, described as "unfounded" by a Saudi Arabia government source, point to a significant escalation of abuses along the perilous "Eastern Route" from the Horn of Africa to Saudi Arabia, where hundreds of thousands of Ethiopians live and work. 

"Saudi officials are killing hundreds of migrants and asylum seekers in this remote border area out of view of the rest of the world," HRW researcher Nadia Hardman said in a statement.

"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."

A Saudi Arabia government source told AFP: "The allegations included in the Human Rights Watch report about Saudi border guards shooting Ethiopians while they were crossing the Saudi-Yemeni border are unfounded and not based on reliable sources."

The New York-based group has documented abuses against Ethiopian migrants in Saudi Arabia and Yemen for nearly a decade, but the latest killings appear to be "widespread and systematic" and may amount to crimes against humanity, it said. 

Last year, UN experts reported "concerning allegations" that "cross-border artillery shelling and small-arms fire by Saudi Arabia security forces killed approximately 430 migrants" in southern Saudi Arabia and northern Yemen during the first four months of 2022.

The HRW report said there was no response to letters it sent to the Saudi interior and defense ministries, the human rights commission and Huthi rebels who control northern Yemen. 

In 2015, Saudi officials mobilized a military coalition in an effort to stop the advance of the Iran-backed Huthis, who had seized the Yemeni capital Sanaa from the internationally recognized government the previous year. 

Yemen's war has created what the United Nations describes as one of the world's worst humanitarian situations.

But many of the abuses described by HRW would have occurred during a truce that took effect in April 2022 and has largely held despite officially expiring last October. 

- Close-range shooting -

The HRW report draws from interviews with 38 Ethiopian migrants who tried to cross into Saudi Arabia from Yemen, as well as from satellite imagery and videos and photos posted to social media "or gathered from other sources". 

Interviewees described 28 "explosive weapons incidents" including attacks by mortar projectiles, the report said. 

Some survivors described attacks at close range, with Saudi border guards asking Ethiopians "in which limb of their body they would prefer to be shot", the report said.

"All interviewees described scenes of horror: women, men and children strewn across the mountainous landscape severely injured, dismembered or already dead," it said. 

One 20-year-old woman from Ethiopia's Oromia region said Saudi border guards fired on a group of migrants they had just released from custody. 

"They fired on us like rain. When I remember, I cry," she said. 

"I saw a guy calling for help, he lost both his legs. He was screaming; he was saying, 'Are you leaving me here? Please don't leave me'. We couldn't help him because we were running for our lives." 

HRW called on Riyadh to "immediately and urgently revoke" any policy of using lethal force on migrants and asylum seekers and urged the UN to investigate the alleged killings.