Vladimir Putin has used a deadly vacuum bomb as part of Russia's invasion of Ukraine, an ambassador has claimed.
The Ukrainian ambassador to the US Oksana Markarova said on Monday the Kremlin had used the devastating bomb - which is banned by the Geneva convention - during air strikes.
"They used the vacuum bomb today, which is actually prohibited by the Geneva convention," Markarova said after briefing members of the U.S. Congress.
"The devastation that Russia is trying to inflict on Ukraine is large."
Western officials feared Moscow would begin using such weapons - dubbed the 'father of all bombs' - if their assault on the former fellow Soviet country faltered.
The high-power thermobaric weapons vaporise bodies and crush internal organs, the Mirror UK reports.
They use the atmosphere itself as part of the explosion and are among the most powerful non-nuclear weapons ever developed.
Such weapons were developed by both the US and the Soviet Union in the 1960s.
In September 2007, Russia detonated the largest one ever made - making it a point of concern for Western forces.
An unnamed official previously told the Daily Star : "My fear would be that if they don't meet their timescale and objectives they would be indiscriminate in their use of violence.
"They don’t adhere to the same principles of necessity and proportionality and rule of law that Western forces do."
It comes as Russia faces deepening isolation and economic turmoil as Western nations, united in condemnation of its assault, attempt to cripple it with an array of sanctions.
Ukraine's allies also increased weapons transfers in support, with Finland agreeing to ship 2,500 assault rifles and 1,500 anti-tank weapons.
Putin's war has rumbled into its second week but things are not quite going to plan
