As head of Russia’s Radiation, Chemical and Biological Protection troops, Igor Kirillov – who has died in an explosion in Moscow – was accused by the West of overseeing the use of chemical weapons on the battlefield in Ukraine.

Sources from Ukraine’s SBU security service said it it was behind the blast and described it as a special operation against a legitimate target.

Kirillov and an aide were killed by explosives planted in an electric scooter, according to Russian officials, which was blown up as he left the building he lived in on Ryazansky Prospekt in south-eastern Moscow.

He had become notorious for outlandish briefings at the Russian defence ministry which prompted the UK Foreign Office to label him as a “significant mouthpiece for Kremlin disinformation”.

Kirillov was far more than just a mouthpiece, heading Russia’s Timoshenko Radiation, Chemical and Biological Protection Academy, before going on to lead the Russian army’s Radiation, Chemical and Biological Protection Troops in 2017.

The force’s main tasks involve identifying hazards and protecting units from contamination but also “causing loss to the enemy by using flame-incendiary means”, the Russian defence ministry says.

The UK Foreign Office said that the force he commanded had deployed “barbaric chemical weapons in Ukraine”, highlighting what it said was the widespread use of riot control agents and “multiple reports of the use of the toxic choking agent chloropicrin”.

On the eve of his killing, Ukraine’s SBU declared that he had been named in absentia in a criminal case for the “mass use” of prohibited chemical weapons on the eastern and southern fronts in Ukraine.

It cited “more than 4,800 cases of the enemy using chemical munitions” on Ukrainian territory since the start of the full-scale Russian invasion in February 2022.

It said toxic substances had been used in drone attacks as well as in combat grenades.

Kirillov earned his notoriety from the start of the war with a series of claims directed towards both Ukraine and the West, none of which were based on fact.

Among his most outrageous claims was one that the US had been building biological weapons laboratories in Ukraine. It was used in an attempt to justify the full-scale invasion of its smaller neighbour in 2022.

He produced documents in March 2022 which he claimed had been seized by Russia on the day of the invasion on 24 February – which were amplified by pro-Kremlin media but rubbished by independent experts.

Kirillov’s notorious allegations against Ukraine continued into this year.

Last month he claimed that “one of the priority aims” of Ukraine’s counter-offensive into Russia’s Kursk border region was to seize the Kursk nuclear power plant.

He presented a slideshow, purportedly based on a Ukrainian report, alleging that in the event of an accident only Russia territory would be exposed to radioactive contamination.

One of Kirillov’s repeated themes was that Ukraine was seeking to develop a “dirty bomb”.

Two years ago he alleged that “two organisations in Ukraine have specific instructions to create a so-called ‘dirty bomb’. This work is in its final stage”.

His claims were rejected by Western countries as “transparently false”.

But Kirillov’s claims prompted Ukraine’s President Volodymyr Zelensky to warn that if Russia suggested Kyiv was preparing that kind of weapon, it meant only one thing – that Russia was already preparing it.

Kirillov returned to his dirty bomb claims last summer, this time alleging the discovery of a chemical weapons laboratory close to Avdiivka, a city in eastern Ukraine that the Russians captured last February.

Kyiv, he claimed, was violating the international Chemical Weapons Convention with a variety of substances with the assistance of Western countries, including the psychochemical warfare agent BZ as well as hydrocyanic acid and cyanogen chloride.

His death is being seen by pro-Kremlin loyalists as a blow, but also as evidence that Ukraine has the ability to target high-profile officials in Moscow.

The deputy speaker of Russia’s upper house of parliament, Konstantin Kosachev, said his death was an “irreparable loss”.