By RICK GLADSTONE

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.

Human Rights Watch and other groups have previously accused Saudi Arabia of using cluster munitions in Yemen, including in a Jan. 6 strike in Sana, the capital, and have criticized the United States as an accomplice.

In a Jan. 12 letter to President Obama, Megan Burke, the director of the Cluster Munition Coalition, a disarmament group, urged him to “demand that Saudi-led coalition members stop using cluster munitions,” and said the United States “should investigate its own role in the recent strikes.”

John Kirby, the State Department spokesman, said in a statement Sunday night: “We have seen the Human Rights Watch report, and are reviewing it. Obviously we remain deeply concerned by reports of harm to civilians and have encouraged the Saudi-led coalition to investigate reports of civilian harm.” Saudi officials did not comment, but have denied ordering the use of cluster munitions in Yemen.

Cluster munitions contain submunitions, or bomblets, that disperse widely and kill indiscriminately. Many bomblets can fail to explode, posing a threat to civilians. A 2008 treaty bans the weapons, but major arms suppliers, including the United States and Russia, have not signed it.

Sensitive to the criticism, the United States has severely restricted exports of cluster munitions and has sought to improve technology to minimize collateral damage. Under a 2009 law, only cluster munitions with a failure rate of 1 percent or less can be exported, and they can be used only against “clearly defined military targets,” not “where civilians are known to be present.”

The latest Human Rights Watch report dwelled on what it described as potential violations of that law, based partly on evidence that one type of American cluster bomb sold to the Saudis, the CBU-105 Sensor Fuzed Weapon, had been used in at least two attacks and had a failure rate exceeding 1 percent. “The evidence raises serious questions about compliance with U.S. cluster munition policy and export rules,” Mr. Goose said.