Human Rights Watch released a report Sunday providing new indications that Saudi Arabia has fired American-made cluster munitions, banned by international treaty, in civilian areas of Yemen, and said their use may also violate United States law.

The report included photographs from Yemen purporting to show unexploded but potentially lethal remnants of American cluster weapons, suggesting that they had failed legally required reliability standards.

If confirmed, the report could put new pressure on the United States over support for its ally Saudi Arabia in the Yemen conflict. The Americans have sold arms and furnished training and expertise to a Saudi-led coalition that has faced widespread criticism for what rights groups call an indiscriminate bombing campaign against Yemen’s Houthi rebels in nearly a year of fighting.

“Saudi Arabia and its coalition partners, as well as their U.S. supplier, are blatantly disregarding the global standard that says cluster munitions should never be used under any circumstances,” Steve Goose, the arms director at Human Rights Watch, said in the report.