Vacuum bombs were reportedly used by the Russian military amid the Ukraine invasion, according to a top diplomat - but what is the weapon and how does it work?

Following a meeting with members of the US Congress, Ukraine's ambassador to the United States Oksana Markarova told the press that Russia had used a thermobaric weapon in its invasion of her country.

There has no further official confirmation over Ms Markarova's claims that thermobaric weapons have been used in the conflict so far.

Better known as a vacuum bomb, thermobaric weapons or warheads use oxygen in the air to create a high-temperature explosion - emitting a deadly shock wave in the surrounding area.

Vacuum bombs can cause slow and painful deaths as the shock wave sucks oxygen from the lungs of anyone in the vicinity.

The blast wave is generally significantly longer in duration than that of a conventional explosive with the capability to vaporise human bodies in moments.

How dangerous is a vacuum bomb?

The US Central Intelligence Agency (CIA) has a study that states vacuum bombs can “obliterate” anybody “near the ignition point”, according to the Independent.

The CIA study reads: “Those at the fringe are likely to suffer many internal, thus invisible injuries, including burst eardrums and crushed inner ear organs, severe concussions, ruptured lungs and internal organs, and possibly blindness.”

A Human Rights Watch report from 2000, citing the US Defence Intelligence Agency, said the pressure wave of a detonated vacuum bomb kills by "rupturing lungs”.

The report added: “If the fuel deflagrates but does not detonate, victims will be severely burned and will probably also inhale the burning fuel.

“Since the most common FAE (fuel-air explosive) fuels, ethylene oxide and propylene oxide, are highly toxic, undetonated FAE should prove as lethal to personnel caught within the cloud as with most chemical agents.”

Another Defense Intelligence Agency document suggests that those hit by the pressure waves could “suffer for several seconds or minutes while they suffocate”.

Russia and Ukraine latest

It comes as Boris Johnson dismissed Vladimir Putin’s announcement that he is putting Russia’s strategic nuclear deterrent on high alert as a “distraction” from struggle his troops are facing in Ukraine.

The Russian leader said on Sunday that he was putting Moscow’s nuclear forces on a “special regime of combat duty” in response to “aggressive statements” coming from Western powers.

Earlier Russian television footage showed Mr Putin meeting with his defence minister and the chief of the general staff, and instructing them to put the nuclear deterrent on a “special regime of combat duty”.

“Western countries aren’t only taking unfriendly actions against our country in the economic sphere, but top officials from leading Nato members made aggressive statements regarding our country,” he said.

But on a day when the expected assault on Kyiv again failed to materialise and the Ukrainians claimed to have driven Russian forces out of the country’s second city Kharkiv, Mr Johnson said his words were “a distraction from the reality of what’s going on”.

“This is an innocent people who are facing a totally unprovoked act of aggression against them, and what’s actually happening is that they are fighting back perhaps with more effect, with more resistance, than the Kremlin had bargained for,” he said.

“You can see some of the logistical difficulties that the Russian forces are experiencing.

“The Russian defence ministry have themselves conceded that they’re having casualties.

“This is a disastrous misbegotten venture by President Putin.”

Meanwhile White House press secretary Jen Psaki accused Mr Putin of resorting to the tactics he used running up to invasion, “which is to manufacture threats that don’t exist in order to justify further aggression”.