Mourners attend a funeral of people killed, mainly children, killed in an Aug. 9 air strike by the Saudi-led coalition on a bus in northern Yemen, in Saada, Yemen. (NAIF RAHMA/Reuters)

The U.S.-backed coalition battling Houthi militants in Yemen has failed to properly investigate alleged airstrikes on civilian targets, a human rights group said Friday, in a campaign already under scrutiny for helping to fuel human suffering on a vast scale.

In a new analysis released early Friday, Human Rights Watch found that an investigatory body overseen by Saudi Arabia, which leads a group of mostly Arab countries engaged in Yemen since 2015, has cleared itself of wrongdoing in most of the nearly 80 incidents it has examined over the past two years.

Publicly released information “shows a general failing . . . to provide credible, impartial, and transparent investigations into alleged coalition laws-of-war violations,” Human Rights Watch said in its report.

Those conclusions, the report found, differ starkly from the picture presented by the news media and civil society groups in Yemen, where coalition aircraft have repeatedly struck civilian targets, including hospitals and funerals. Most recently, at least 40 children died in a coalition strike on a bus in northern Yemen on Aug. 9.

The Houthi rebels, which Gulf and Western nations allege receive weaponry and other support from Iran, have meanwhile fired missiles at Saudi Arabia and are blamed for contributing to a conflict that has generated a massive humanitarian crisis.

After completing almost 80 investigations, the Saudi-led coalition’s Joint Incidents Assessment Team (JIAT), formed with U.S. assistance in 2016, acknowledged problems with only 11 cases and found just one in which forces affiliated with the coalition had violated rules of engagement, Human Rights Watch said.

The vast majority of the JIAT investigations concluded that any strikes on civilians were unintentional outcomes of legitimate military operations, the analysis found, “and did not appear to consider whether the attack was lawfully proportionate or if precautions taken were adequate.”

JIAT investigators called for the coalition to provide assistance in about 10 instances when technical or intelligence errors or other factors such as weather contributed to strikes on civilian targets.

The JIAT, which is made up of officials from the coalition countries, recommended further investigation or disciplinary action in two incidents, the analysis said.

Human Rights Watch based its analysis on public statements by a JIAT spokesman and reporting by the Saudi press agency.

The analysis comes as the Trump administration faces increasing pressure from lawmakers over its support to the coalition, which includes arms sales, intelligence sharing and aerial refueling of coalition planes operating in Yemen.

A new defense law links the refueling to the administration’s ability to certify that Saudi Arabia and its allies are taking steps to protect civilians and end the war. Legislators from both parties have voiced mounting exasperation with the conflict and its toll on Yemenis — both from the air campaign and a sharp increase in poverty, malnutrition and disease.

Critics say the United States may be exposing itself to being held legally responsible for attacks on civilians in Yemen.

Human Rights Watch urged Saudi Arabia and its allies to improve its investigatory procedures, extend condolence payments where necessary, and “appropriately prosecute people responsible for war crimes.”

It also called for a suspension of arms sales to Saudi Arabia, a major customer for Western weaponry. President Trump announced massive arms sales to the kingdom during his inaugural foreign trip last year.

“Governments selling arms to Saudi Arabia should recognize that the coalition’s sham investigations do not protect them from being complicit in serious violations in Yemen,” said Sarah Leah Whitson, the group’s Middle East director.

The United States has also been criticized for its handling of civilian deaths caused by U.S. air operations. The official military tally of civilians killed in the U.S. campaign against the Islamic State in Iraq and Syria is a fraction of estimates given by watchdogs.