CAIRO — By arming and backing a Saudi-led coalition fighting in Yemen, the United States, Britain and France may be complicit in potential war crimes, the United Nations said in a scathing report Tuesday that called for more accountability from all sides in the war.

The wide-ranging report from a team of investigators commissioned by the U.N. Human Rights Council found that all parties to the conflict had perpetrated possible war crimes through airstrikes, shelling, snipers and land mines, as well as arbitrary killings, torture and other abuses.

The Saudi-led coalition, which is aligned with Yemen’s internationally recognized government, is accused of intentionally starving Yemenis as a tactic of war and killing thousands of civilians in airstrikes. The coalition’s foes, northern rebels known as Houthis, are accused of planting land mines, shelling cities and deploying child soldiers.

The Post's Sudarsan Raghavan visited Yemen in late May to report on what the United Nations describes as the world's most severe humanitarian crisis. (Sudarsan Raghavan, Joyce Lee, Ali Najeeb/The Washington Post)

The U.N. report also strongly challenges the credibility of the Saudi-led coalition to self-investigate and hold itself accountable for attacks that kill civilians. That assurance, routinely given by the Saudis after every attack, is often cited by Trump administration and British officials to justify the continued military support and arms sales to the coalition.

 Representatives for the coalition, the Houthis, the United States, France and Britain were not immediately available for comment.

Human rights groups have long said that the United States, Britain and other Western powers are abetting in prolonging the war and suffering in Yemen, which is on the brink of famine. Earlier this year, Human Rights Watch called on France to “stop fueling Saudi war crimes in Yemen.”

Campaigns by U.S. and British lawmakers, as well as activists, have led to bipartisan measures in the U.S. Congress and court hearings in Britain seeking to stop the arms sales and other assistance to the coalition, especially following the killing of Washington Post contributing columnist Jamal Khashoggi inside the Saudi Consulate in Istanbul last year. So far, those efforts have proved unsuccessful.

While most of the abuses detailed by the investigators have been previously reported by journalists and human rights groups, the U.N. report is striking for its broad demand for accountability. 

The investigators highlighted what many of the war’s critics describe as the destructive role played by the United States, Britain and France — all permanent U.N. Security Council members. The United States, in particular, provides logistical support and intelligence to the coalition, in addition to selling billions of dollars in weaponry to the group, which is also led by the United Arab Emirates. 

The report also accused Shiite-led Iran of helping to perpetrate war crimes through its support for the Shiite Houthis. 

Such “third states” that “directly or indirectly” have influence on Yemen’s warring parties “may be held responsible for providing aid or assistance for the commission of international law violations,” the report said.

“The legality of arms transfers by France, the United Kingdom, the United States and other States remains questionable, and is the subject of various domestic court proceedings,” it said.

The report comes two days after the coalition launched an airstrike on a rebel prison, killing more than 100 people. On Monday, a group of Republican and Democratic lawmakers began a fresh push to stop U.S. logistical support for the coalition’s air campaign and certain forms of intelligence sharing.

The U.N. investigators have sent a list of individuals “who may be responsible for international crimes” to the U.N. human rights commissioner, Michelle Bachelet. But it remained unclear whether the list included any Westerners. In the report’s appendix, investigators listed the names of more than 160 key actors in Yemen’s war — all Yemeni, Saudi or Emirati nationals — but did not state whether any of them have committed potential war crimes.

The coalition has been battling the Houthis, who took control of the Yemeni capital in September 2014, since March 2015 in an effort to restore Yemen’s internationally recognized government and prevent Tehran from expanding its regional influence. The conflict has worsened a humanitarian crisis in the region’s poorest country that has left more than 24 million people — roughly 80 percent of the population — in need of assistance.

 By some estimates, the conflict has killed as many as 95,000 people, including tens of thousands of civilians, violating international humanitarian laws.

Time and again, the Saudi-led coalition has promised to investigate such alleged violations through its internal Joint Incidents Assessment Team. But coalition airstrikes on civilian targets — hospitals, clinics, markets, even school buses carrying children — have been unrelenting.

After reviewing the assessment team’s latest conclusions, the U.N. investigators found that the team did not expressly hold the coalition responsible for any violation. That, the report said, “raises concerns as to the impartiality of its investigations and the thoroughness and credibility of its analysis and findings.”

“The assessment of the targeting process is particularly worrying, as it implies that an attack hitting a military target is legal, notwithstanding civilian casualties, hence ignoring the principle of proportionality,” the report added.

“Five years into the conflict, violations against Yemeni civilians continue unabated, with total disregard for the plight of the people and a lack of international action to hold parties to the conflict accountable,” Kamel Jendoubi, the Tunisian head of the U.N. investigation, said in a statement. “The international community must multiply its efforts to free the Yemeni people from the persistent injustice they have been enduring.”