Cluster bombs have a high dud rate, which means they have had a failure rate of up to 40%.
Controversial cluster munitions supplied by the United States are being used by Ukraine in their counteroffensive against Russia, a White House spokesman John Kirby has said. "We have gotten some initial feedback from the Ukrainians, and they're using them quite effectively," White House national security spokesman John Kirby told reporters on Thursday.
Although Moscow, which had earlier said it would use "similar" weapons if the United States supplied cluster bombs to Ukraine, is yet to react to the announcement, the claim by the White House official has triggered outrage from some allies and humanitarian groups.
What are cluster bombs?
A cluster bomb opens in the air and releases smaller "bomblets" across a wide area. The bomblets are designed to take out tanks and equipment, as well as troops, hitting multiple targets at the same time.
But what makes their use a source of concern is that they have a high dud rate, which means they have had a failure rate of up to 40%, leaving the ground littered with unexploded bomblets. Washington says the cluster munitions it is sending to Ukraine have a failure rate of less than 2.35%.
Is using cluster bombs a war crime?
The use of cluster bombs itself does not violate international law, but using them against civilians can be a violation. As in any military conflict, determining a war crime requires looking at whether the target was legitimate and if precautions were taken to avoid civilian casualties.
More than 120 countries have joined Convention on Cluster Munitions, agreeing not to use, produce, transfer, or stockpile the weapons. The US, Russia, and Ukraine, however, have not signed the agreement.
Where have they been used?
Cluster bombs have been deployed in many recent conflicts, including where US forces were involved.
According to Human Rights Watch, both Moscow and Kyiv have used cluster munitions during the nearly 17-month conflict in Ukraine, which Russia calls a "special military operation".
Cluster bombs were also used by the Syrian government troops against opposition strongholds during the country's civil war, frequently hitting civilian targets and infrastructure.
Israel has also been criticised for its use in civilian areas in south Lebanon, including during the 1982 invasion. According to HRW, Israel fired as many as four million cluster munitions into Lebanon during its month-long war with Hezbollah in 2006.
The Saudi-led coalition in Yemen reportedly also used cluster bombs in the war with the Iran-backed Houthi rebels that has ravaged the southern Arabian country.
The US has also used the weapons during the invasion of Afghanistan. During the first three years of the conflict, the US-led coalition is estimated to have dropped more than 1,500 cluster bombs in Afghanistan.