Russia has been accused of using everything from so-called vacuum bombs to chemical weapons as it fights to overtake Ukraine.
Some of the worst weapons that Moscow has allegedly used are indiscriminate in their nature, prompting concerns about their impact on civilian populations from Ukrainian officials, the West, and human rights groups monitoring the war.
“There is deliberate targeting of civilian populations and noncombatants, which is against international law,” said John Erath, senior policy adviser for the Center for Arms Control and Nonproliferation. “And it really does not matter what type of weapon is being used. That is really bad.”
Here are five of the worst weapons Russia has been accused of using in its invasion.
Cluster munitions
Cluster munitions, which are designed to be used against multiple targets at once, consist of a container from which many smaller submunitions and bombs are scattered over a wide area.
In addition to the threat they pose when launched, sometimes the smaller munitions fail to detonate on impact — resulting in a new threat to civilians that can last even after the initial conflict ends.
The Convention on Cluster Munitions, which became binding international law in 2010, bans the use of the weapons. To date, 123 countries have become parties to the treaty, although Russia, Ukraine and the U.S. are not among them.
Allegations that Russia was using cluster munitions against Ukraine first emerged in the early days of the war, when human rights organizations like Human Rights Watch and Amnesty International reported that Russian forces used the weapons days into the war.
By Wednesday, March 30, United Nations Human Rights chief Michelle Bachelet said there were “credible allegations” that Russian forces used cluster munitions at least 24 times, noting that the organization was also looking into allegations that they were being used by Ukrainian forces.
Thermobaric weapons
Thermobaric weapons, often referred to as “vacuum bombs,” consist of a fuel container with two separate explosive charges, according to the Center for Arms Control and Non-Proliferation.
When the weapon is dropped or launched, the first charge detonates to disperse fuel particles, and then the second charge ignites the dispersed fuel and oxygen, creating a second wave of extreme pressure and heat that can create a partial vacuum in a confined space.
There is more than one type of thermobaric weapon, Erath said. He noted that Russia is using barrel bombs, which are typically dropped from an aircraft or helicopter.
Ukrainian Ambassador to the U.S. Oksana Markarova told reporters on Feb. 28 that Russia had used vacuum bombs earlier that day.
On March 9, the U.K. Ministry of Defense tweeted that Russia had confirmed the use of the TOS-1A system, a rocket launcher that can fire rockets with thermobaric warheads.
Chemical weapons
The U.S. and allies have expressed a fear that Russia could deploy chemical weapons against Ukrainian troops and civilians, but have held back from confirming reports that emerged early last week that the banned weapons were deployed in the city of Mariupol.
Michael Carpenter, U.S. ambassador to the Organization for Security and Cooperation in Europe, said on April 13 that there has been “credible information” that Russian forces “may have used” a mix of riot control agents, like tear gas, mixed with chemical agents to incapacitate Ukrainian fighters and civilians.
But his remarks were walked back by the State Department hours later, with State Department spokesperson Ned Price saying Carpenter was referring to information that Russian forces were stockpiling the weapons and capable of carrying out such an attack, but not that the U.S. could confirm they had done so.
“We are engaged in direct conversations with our partners to try and determine what exactly has transpired in Mariupol,” a State Department spokesperson told The Hill on Monday.
The allegation of chemical weapon use was made on April 11 by the far-right Ukrainian paramilitary group Azov Battalion, but was not confirmed independently.
Matthew Kroenig, director of the Atlantic Council’s Scowcroft Strategy Initiative, said it was unclear what agent could have been used, but said it falls into a possible Russian playbook of testing the level of the international response.
“It might be what’s sometimes referred to as ‘salami slicing’ by [Russian President Vladimir] Putin, try a little bit and see what the response is, if there’s no major response, do a little bit more, no major response, to a little bit more — trying to see how much he can get away with,” he said.
Hypersonic missiles
Russia claimed on March 19 that it fired a hypersonic weapon on an underground weapons storage facility in the Ukrainian village of Deliatyn in the Ivano-Frankivsk region.
The Pentagon wasn’t able to verify or refute the claim at that time. Defense Secretary Lloyd Austin even told CBS’s “Face the Nation” that while hypersonic missiles would have been an escalation in the war, he “would not see it as a game-changer.”
However, U.S. European Commander Tod Wolters told the Senate Armed Services committee on March 29 that Russia has launched “multiple” hypersonics in Ukraine.
“There have been multiple launches. Most of them have been directed toward military targets,” Wolters said.
Hypersonics can travel at roughly five times the speed of sound, making them difficult to detect.
Washington has been racing to keep up with Russia and China, which also turned heads with a hypersonic weapons test late last year.
Around the same time Russia claimed to launch its hypersonic in Ukraine last month, the U.S. also successfully tested a hypersonic missile, but kept it quiet to avoid escalating tensions with Russia.
Fléchettes
The Washington Post reported on Monday that Russia may have used small projectiles called fléchettes in an incident in late March.
The 3-centimeter projectiles, which were used in World War I and in Vietnam, likely came from a Russian munition that could carry the projectile.
The weapons have been controversial due to their indiscriminate nature, but they are not explicitly banned by international conventions.