A US-made bomb was used in the deadly attack on a hospital affiliated with Doctors without Borders (MSF) in northern Yemen in August, Amnesty International said Monday.
"According to independent weapons experts consulted by the organization, ... a US-made precision-guided Paveway-series aerial bomb was used in the attack," Amnesty said in a statement.
Philip Luther, a research director for the Middle East and North Africa at Amnesty, said the revelation should trigger a comprehensive embargo on weapons to Yemen and an international investigation to bring those responsible for the attacks to justice.
The watchdog called on states - including the US and UK - "to immediately stop supplying weapons that could be used in the Yemen conflict."
MSF said the August bombing of the Abs Rural Hospital it supported in Hajjah province killed 19 people. Amnesty's Monday report said the attack had killed 11 people and injured 19 others.
The attack was the fourth in 10 months on an MSF facility in Yemen, Amnesty said. The attack prompted the organization to shut down its operations at six hospitals in northern Yemen a few days later.
The hospital had treated 4,611 patients since MSF began to support it in July 2015.
Human rights groups have repeatedly accused the Saudi-led coalition of striking civilian sites in Yemen.
Yemen's conflict has intensified since March 2015, when the Iran-allied Shiite Houthi rebels advanced on the southern city of Aden, prompting Saudi Arabia and fellow Sunni allies to start an air campaign in Yemen against the group.
Saudi Arabia fears that the rebels will give its regional rival, Shiite Iran, a strategic foothold on the Arabian Peninsula.