Amnesty International says the United States used cluster bombs on a cruise missile in Yemen, killing 55 people, most of whom were civilians.

The attack, according to the rights group, targeted Al-Maajala in the Abyan province at a time when Washington was pushing hard to project militants in the country.

“Amnesty International is gravely concerned by evidence that cluster munitions appear to have been used in Yemen,” said Mike Lewis, the group’s arms control researcher, AFP reported.

The group cited a Yemeni parliamentary committee as reporting in February that the attack had killed 41 local residents, including 14 women and 21 children, in addition to 14 alleged militants.

Deputy Director of AI’s Middle East and North Africa Program, Philip Luther warned that “a military strike of this kind against alleged militants without an attempt to detain them is at the very least unlawful.”

“The fact that so many of the victims were actually women and children indicates that the attack was in fact grossly irresponsible, particularly given the likely use of cluster munitions,” he also said.

Lewis said, “Cluster munitions have indiscriminate effects and unexploded bomblets threaten lives and livelihoods for years afterwards.”

AI had obtained photographs which showed remains of the BGM-109D Tomahawk land-attack cruise missile. “This type of missile, launched from a warship or submarine, is designed to carry a payload of 166 cluster sub-munitions (bomblets) which each explode into over 200 sharp steel fragments that can cause injuries up to 150 meters (about 500 feet) away,” an AI statement said.

“An incendiary material inside the bomblet also spreads fragments of burning zirconium designed to set fire to nearby flammable objects,” it added.