An international rights group urged Western governments Wednesday to stop supplying weapons to parties to the conflict in Yemen after reports that they were ending up in the hands of militant groups.

Amnesty International's arms control and human rights researcher Patrick Wilcken said in a statement that "the proliferation of unaccountable, UAE-backed militias is worsening the humanitarian crisis and posing a growing threat to the civilian population." Wilcken said American and British weapons have ended up in the hands of al-Qaida and Daesh militants, in reference to recent reports by the Amman-based Arab Reporters for Investigative Journalism. An Associated Press report last August uncovered deals struck between the coalition and al-Qaida, during which weapons and cash passed from Gulf commanders and their allies to al-Qaida-linked militants fighting alongside them against the rebels.

The U.S. is, by far, the largest supplier of weapons to Saudi Arabia and the UAE, and its support for the coalition has been crucial to the war in Yemen. According to the U.S. Department of Defense, transferring military equipment to third parties breaks the terms of the Saudi-led coalition's arms deals with the U.S. Following the report, a U.S. defense official confirmed that an investigation into the issue was ongoing. Germany, the Netherlands and Norway have restricted arms deals to coalition members, while several other Western countries, including the U.S. and Britain, have continued supplying weapons. Yemen has been wracked by conflict for the last five years when Shiite Houthi rebels overran much of the country. Saudi Crown Prince Mohammed bin Salman, the former Saudi defense minister, and Saudi Arabia's allies launched Operation Decisive Storm in March 2015. Civilians have borne the brunt of the conflict. The last available U.N. figure for the civilian death toll was published in 2016 and stood at more than 10,000. The Armed Conflict Location & Event Data Project, which tracks violence in Yemen, puts it at around 57,000 people. The war has damaged Yemen's infrastructure, crippled its health system and pushed the Arab world's poorest country to the brink of famine.