A defence expert has warned of major Russian retaliation after a senior Russian general in charge of nuclear protection forces died in Moscow on Tuesday (17 December).
Igor Kirillov was killed outside an apartment building on Ryazansky Prospekt.
His assistant was also killed, a Russian investigative committee said.
Ukrainian prosecutors had charged Kirillov with the use of banned chemical weapons in the Ukraine war the day before he died.
Tobias Ellwood, an army reservist and former defence minister, told Sky News on Tuesday: "This will be an embarrassment for Putin. He cannot hide this from the Russian people.
"I would expect a major retaliation on the Russian side."