A high-ranking general in the Russian armed forces and his assistant have been killed in Moscow by Ukraine's security service, a Ukrainian source has told the BBC.
Lt Gen Igor Kirillov, head of the Nuclear, Biological, Chemical Defence Forces (NBC), was outside a residential block early on Tuesday when a device hidden in a scooter was detonated remotely, Russia's Investigative Committee (SK) said.
A source in Ukraine's SBU security service claimed Kirillov was "a legitimate target" and alleged he had carried out war crimes.
On Monday, the SBU charged Kirillov, 54, in absentia, saying on Telegram that he was "responsible for the mass use of banned chemical weapons".
ReutersThe Ukrainian government has not yet commented on the general's death.
Pictures from the scene in south-eastern Moscow showed the badly damaged entrance to a building with scorch marks on the walls and a number of windows blown out. Two body bags could also be seen on the street.
The block was cordoned off on Tuesday morning as Russian investigators continued combing the area.
In October, the UK placed sanctions on Kirillov, saying he had overseen the use of chemical weapons in Ukraine and acted as a "significant mouthpiece for Kremlin disinformation".
Ukraine's SBU has claimed Russia used chemical weapons more than 4,800 times under the general's leadership.
Moscow denies the allegations.
The SK said it had "opened a criminal case into the murder of two servicemen".
"Investigators, forensic experts and operational services are working at the scene," it said.
"Investigative actions and operational search activities are being carried out aimed at establishing all the circumstances of the crime."
Russian state news agencies reported that the explosive device - which killed Kirillov and his aide in Ryazansky Avenue - had an explosive force equivalent to 300g (0.7lb) of TNT.
They added that bomb experts and specialist search dogs had inspected the surrounding area and no other explosives had been found.
Experts have told BBC Verify that judging from images of the scene, it appears the explosion was caused by an Improvised Explosive Device (IED), a type of homemade bomb which usually contains easily obtainable components, such as nails or glass.
APAssassinations of senior officials have been carried out in Russia before, but attacks in Moscow are rare.
Liza, who lives one building away from the site of the blast, told the BBC that while she was not entirely surprised, the killing of Igor Kirillov was a "shocking" development.
"It's one thing reading about it in the news, it feels far, but when it happens next door, that's completely different and frightening," she tells me.
"Until now, [the war] felt as if it was happening a long way off – now someone is dead, here, you can feel the consequences," Liza said, adding that "unfortunately, I don't think things will calm down any time soon".
Several other local residents said they initially thought the loud noise they heard had come from a construction site.
Student Mikhail Mashkov, who lives in the building next door, told the AFP news agency he was woken up by a "very loud explosion noise", thinking "something fell at the construction site", before looking outside.
Olga Bogomolova said she thought a container had fallen at the construction site but then realised "it was a very strong explosion", saw "broken windows" and that it was something else.
People living in the area told the BBC of their deep sense of shock.
Even after nearly three years since Russia's full-scale invasion of Ukraine, for many Muscovites, the war is something that is happening a long way away - something they only see on TV or on their phones.
The killing of a Russian general in Moscow is a sign that this war is very real and very close to home.
EPA-EFE/REX/ShutterstockUnder UK sanctions, Kirillov was subject to an assets freeze and travel ban.
In May, the US accused Russia of deploying chemical weapons as a "method of warfare" in Ukraine, in violation of international laws banning their use.
State department officials said Russia used the choking agent chloropicrin to win "battlefield gains" over Ukraine.
According to the SBU, Russian forces have used drones to drop chemical weapons on Ukrainian soldiers.
Ukrainian Col Artem Vlasiuk had previously said that more than 2,000 Ukrainian service members had been treated in hospital for chemical poisoning over the course of the war and three people had died.
The Kremlin rejected the accusations at the time, calling them "baseless".
Kirillov served in different roles in Russia's military associated with hazardous materials, including the Directorate of the Chief of the Radiation, Chemical and Biological Defence Troops.
He was appointed head of the NBC in 2017.
Reacting to Kirillov's death, UK Prime Minister Sir Keir Starmer's official spokesman said: "Clearly we are not going to mourn the death of an individual who has propagated an illegal invasion and imposed suffering and death on the Ukrainian people."
Ukraine's Security Services appear to be stepping up their targeting of senior Russian individuals, almost three years into the conflict.
Kirillov's death comes less than a week after a prominent Russian weapons expert was shot dead near his home in Moscow.
Ukrainian media reported that the assassination of Mikhail Shatsky was carried out by Ukraine's military intelligence service.
Senior Russian naval officer Valery Trankovsky and Russian prison boss Sergei Yevsyukov also died after car bombs exploded in Russian-occupied Ukraine in recent weeks.
