What Are Cluster Munitions, Vacuum Bombs? Russia Accused of Using the Weapons in Ukraine

As Russia's invasion of Ukraine continues, reports have emerged that Russian forces have used cluster bombs and vacuum bombs—weapons that have been denounced by over 100 countries worldwide.

On February 25, the charity Human Rights Watch reported that four civilians were killed and 10 wounded when a Russian cluster bomb struck near a hospital in the Ukrainian town of Vuhledar the previous day.

The charity said it had interviewed hospital workers who had supplied photographs of some of the dead, while there were also photos posted to social media verifying the attack.

Steve Goose, arms director for Human Rights Watch, called the attack "callous" and called on Russia to stop using weapons "that indiscriminately kill and maim."

Oksana Markarova, Ukraine's ambassador to the U.S., told reporters that Russian forces had used a vacuum bomb, according to Reuters, though there has been no official confirmation of this. CNN reported that a team of its journalists had spotted a TOS-1 rocket launcher capable of launching thermobaric warheads.

In a White House press briefing on Monday, press secretary Jen Psaki said that if reports of such weapon use were true, "it would potentially be a war crime."

What Are Cluster Bombs?

Cluster bombs or cluster munitions are a type of explosive that contain many other, smaller explosives. These smaller explosives, also called sub-munitions or bomblets, spread over a wider area than a traditional bomb would. This decreases the bomb's accuracy but increases its area of effect.

Cluster bombs are widely condemned by human rights organizations since they have killed and injured thousands of civilians, according to conflict charity Humanity and Inclusion.

Another reason they are so dangerous is that many of the sub-munitions—up to 40 percent, by one estimate—do not end up exploding on impact. Instead, they remain embedded in the ground or buildings, ready to detonate at any moment.

Under the Convention on Cluster Munitions, a total of 123 countries worldwide have agreed never to use cluster munitions under any circumstances nor to develop, stockpile, or sell them. This includes Canada, much of Western Europe, Australia, much of Africa and numerous South American countries.

However, neither the U.S., Russia, or Ukraine have committed to this agreement.

What Are Vacuum Bombs?

Vacuum bombs, also known as thermobaric explosives, are used to produce large, very hot explosions.

They work in two stages. First, an explosion occurs which sends a cloud of fuel or dust-like material into the air. The cloud then ignites, producing a fireball and a shockwave which expands in all directions.

Since the fire consumes the oxygen from the surrounding air, the explosion and initial shockwave leaves behind a vacuum and causes a negative pressure wave which can cause trauma of the lungs, according to one study. The weapons can be very effective in enclosed areas such as tunnels or buildings.

Thermobaric weapons have been used by both Russia and the U.S., The Guardian newspaper reports.

A soldier in Ukraine
A soldier in Ukraine stands guard in the town of Avdiivka on February 9, 2022. Russia has been accused of using cluster bombs and vacuum bombs in Ukraine. Will Vassilopoulos/AFP/Getty