The United Nations issued a report Tuesday that blames all factions involved in the Yemen conflict for civilian deaths, torture of detainees, rape and other violent offenses that could be considered international war crimes.

Iran-backed Houthi rebels have for years battled for control of Yemen, and a Saudi-led coalition is fighting in support of the ousted government under President Abdrabbuh Mansur Hadi, who fled the country in 2015. It’s created what U.N. Secretary-General Antonio Guterres and others have described as “the world’s worst humanitarian crisis.”

The 41-page report from the so-called Group of Experts, established by the U.N.’s Human Rights Council, cataloged acts of violence that occurred between September 2014 and June 2018. Here’s what we know.

What the report found

The group, made up of three regional specialists from Tunisia, Australia and the UK, visited at least four Yemeni cities to document accounts of residents and alleged victims.

Their findings include:

Airstrikes hitting residential sites, such as markets, weddings and medical facilities, are causing most of the civilian deaths. Since the conflict began in March 2015, an estimated 6,600 civilians have been killed and another 10,563 have been injured, according to the Office of the United Nations High Commissioner for Human Rights. The U.N. and other humanitarian groups have said the death toll is likely much higher.

Since the conflict began in March 2015, an estimated 6,600 civilians have been killed and another 10,563 have been injured, according to the Office of the United Nations High Commissioner for Human Rights. The U.N. and other humanitarian groups have said the death toll is likely much higher. The Yemen government and coalition of forces, including Saudi Arabia and the United Arab Emirates, are conducting the airstrikes, the group said. “The intensity of the air campaign has been unceasing, even after its impact on the civilian population became apparent,” according to the U.N. report, which also implicated rebels in indiscriminately killing civilians when it engages in urban warfare.

“The intensity of the air campaign has been unceasing, even after its impact on the civilian population became apparent,” according to the U.N. report, which also implicated rebels in indiscriminately killing civilians when it engages in urban warfare. Yemen’s government, coalition forces and Houthi rebels are enlisting children as young as 8 years old into the fight. The group also documented rapes of male detainees by UAE personnel, and of women in a migrant detention facility in Aden by government-controlled security forces.

Who is responsible?

“The primary legal responsibility for addressing these violations and crimes lies with the government of Yemen, which bears the duty to protect persons under its jurisdiction,” said Kamel Jendoubi, the group’s chairman. “I call upon the government of Yemen to investigate and prosecute violations that amount to crimes by their nationals and armed forces.”

Defense Secretary Jim Mattis on Tuesday defended the U.S. backing of the Saudi-led coalition, but said it was conditioned on the Saudis doing “everything humanly possible” to avoid civilian casualties.

“For the last several years we have been working with the Saudis and the Emiratis, doing what we can to reduce any chance of innocent people being injured or killed,” he said.

Why it matters

More than 22 million people — three-quarters of the population — in Yemen are in need of aid, according to Guterres.

Earlier this month, an airstrike hit a school bus driving through a market in a rebel stronghold in northern Yemen, killing dozens, including 40 children. The Saudi-led coalition said it was targeting rebels who had fired a missile at Saudi Arabia. The military coalition is investigating the incident.

The top U.S. commander in the Middle East and Southwest Asia, Lt. Gen. Jeffrey Harrigian, who is stepping down this week, did not comment on the school bus strike in an interview with The New York Times, citing the ongoing investigation. But, he said, “clearly, we’re concerned about civilian casualties, and they know about our concern,” referring to Saudi officials.

Kristine Beckerle, the Yemen researcher at Human Rights Watch, which recently issued its own report, said on Friday’s PBS NewsHour that the U.S. has been “tight-lipped” about the kind of support it is providing the coalition.

“What we do know is they are providing this midair refueling, but the U.S. won’t tell us which aircraft, for example, it refueled. Did it refuel the coalition aircraft that bombed a market, a home, a hospital, a wedding?” she said.

The U.N. report says further investigation of violations and abuses is required.