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Eliot Higgins, founder of open-source journalism site Bellingcat, says Russia has been using cluster bombs -- widely banned artillery rounds that indiscriminately shower a target area in a deadly rain of "bomblets" -- every day in its war on Ukraine.
Tracking launch positions with satellite imagery, Higgins told Newsy, his team has been able to determine "some of these are being launched from inside Russia into Ukrainian towns and cities."
Cluster munitions detonate in midair and release smaller projectiles powerful enough to kill a person or destroy a vehicle. The submunitions can often fail to detonate on impact, making them a threat long after hostilities have ceased.
Humanitarian organizations first reported that Russian military forces were using cluster munitions in late February on at least two civilian areas in Ukraine, including a preschool.
Three people were killed on Feb. 25 when a 220mm Uragan rocket dropped a cluster bomb on the Sonechko kindergarten in Okhtyrka in northeastern Ukraine, according to Amnesty International. A day earlier, a missile carrying cluster munitions reportedly exploded outside a hospital in eastern Ukraine.
Four civilians were killed, according to Human Rights Watch, and another 10 were injured, including six health care workers.
Here's what you need to know about cluster bombs, including why they're so dangerous, whether Russia could be considered guilty of war crimes for using them and whether the US has joined in banning their use.
What are cluster bombs?
Launched from the ground or dropped from the air, cluster bombs are a type of explosive that detonates in flight and release dozens or even hundreds of submunitions over a wide swath.
A single cluster bomb attack can "saturate an area up to the size of several football fields," according to the Cluster Munition Coalition, which campaigns against their use. That makes them the weapon of choice for forces looking to inflict damage as widely as possible.
While many cluster bombs are designed to kill personnel and destroy vehicles, some are intended to take out power lines or disperse land mines or chemical weapons.
Why are cluster munitions so dangerous?
Cluster munitions are incredibly indiscriminate in their targeting, often maiming or killing civilians.
Often the submunitions don't explode on impact, posing a threat long after hostilities have ceased. According to the International Red Cross, cluster munitions can have a dud rate of up to 40%.
More than 1,200 Kuwaitis have been killed by cluster munitions since the end of the first Gulf War 30 years ago. In Vietnam, hundreds of civilians are wounded or killed every year by cluster bombs left behind by US and Viet Cong forces in the 1970s.
The bombs are banned by an international treaty signed by dozens of countries. Though neither Russia nor Ukraine is among them, using cluster munitions on civilians is considered a war crime by the International Criminal Court.
Is Russia using cluster bombs in Ukraine?
Humanitarian groups were the first to accuse Russia of using cluster bombs in its assault on Russia, an allegation supported by NATO's secretary-general.
Human Rights Watch says it has verified photographs submitted by hospital staff and posted to social media that show the nose cone and antenna of a 9N123 cluster munition warhead delivered by a 9M79-series Tochka ballistic missile.
Such warheads contain 50 submunitions, HRW reported, each of which contains 3.1 pounds of explosives and shatters into approximately 316 uniform fragments.
Amnesty International shared drone footage it says shows evidence of cluster munition damage on more than a half-dozen spots around a kindergarten in Okhtyrka, including on the building's roof and sidewalk.
The strike "may constitute a war crime," Amnesty International said in a statement.
The organization pointed to reporting from the open-source investigative site Bellingcat that indicates the remains of a 9M27K rocket were discovered 650 feet to the east of the school. With a range of about five to 20 miles, 9M27K rockets are packed with 30 submunitions, each of which carries more than a half-pound of explosives and shatters into up to 400 fragments.
On Friday, NATO Secretary-General Jens Stoltenberg said officials "have seen the use of cluster bombs and we have seen reports of use of other types of weapons which would be in violation of international law."
US Ambassador to the United Nations Linda Thomas-Greenfield told the UN last week that video footage shows Russian forces moving "exceptionally lethal weaponry" into Ukraine.
"That includes cluster munitions and vacuum bombs -- the use of which directed against civilians is banned under the Geneva Conventions," Thomas-Greenfield added.
Russia has not commented on whether it is using the controversial munitions. Kremlin press secretary Dmitry Peskov has said civilian deaths are being caused by right-wing Ukrainian nationalist groups putting military equipment in populated areas and using civilians as human shields.
Both the Ukraine military and Russia-backed separatists used cluster bombs during a 2015 conflict in eastern Ukraine, according to a Human Rights Watch report, though Ukraine has denied that allegation.
What is the Convention on Cluster Munitions?
In 2008 the Convention on Cluster Munitions -- a treaty prohibiting the use, production or stockpiling of the weapons -- was signed by 120 nations, including Canada, Australia and numerous European nations.
Signatories also included several countries where such weapons have been used, such as Lebanon, Laos and Afghanistan.
"There is no possible justification for dropping cluster munitions in populated areas," Amnesty International Secretary-General Agnès Callamard said of the attack on the preschool in Okhtyrka, adding that it "shows flagrant disregard for civilian life."
Countries that declined to sign the treaty and continue to produce or amass cluster weapons include China, Brazil, Israel, India and Pakistan. Neither Russia nor Ukraine has signed the treaty.
Has the US signed the ban on cluster bombs?
To date, the US has refused to join the Convention on Cluster Munitions. In 2008, President George W. Bush's administration declared the bombs were "legitimate weapons with clear military utility in combat."
A 2008 Department of Defense directive ordered that all submunitions produced by the US had to have a failure rate of less than 1%. But in November 2017, a new policy under President Donald Trump allowed the use of cluster munitions that didn't meet that 1% threshold "in extreme situations to meet immediate warfighting demands."
The US last used cluster munitions during the 2003 invasion of Iraq, according to the Landmine and Cluster Munition Monitor, "with the exception of a single attack in Yemen in 2009."
The US has an estimated stockpile of 1 billion submunitions, though it only manufactures new cluster munitions for foreign sale, according to the Arms Control Commission.
What is a vacuum bomb?
On Monday, Ambassador of Ukraine to the US Oksana Markarova accused Russia of deploying vacuum bombs.
Consisting largely of fuel, vacuum bombs (also known as thermobaric weapons), suck in oxygen from the surrounding atmosphere and explode in a high-temperature fireball that can vaporize a human body.
While cluster bombs are used to devastate widespread areas, vacuum bombs generally target harder-to-reach sites like bunkers, tunnels and foxholes.
There has not been official confirmation that vacuum bombs have been used in the conflict in Ukraine, though on Feb. 26 a CNN crew reportedly spotted a Russian thermobaric multiple rocket launcher near Ukraine's border.
Is there a ban on vacuum bombs?
Unlike cluster munitions, there is no international treaty specifically banning thermobaric weapons. But the use of weapons that don't discriminate between civilians and military targets are broadly banned by the Geneva Conventions.
While neither Russia nor Ukraine is subject to the International Criminal Court, ICC prosecutor Karim Khan said he was opening an investigation into the possibility of war crimes being committed during the invasion.