The death of a high-ranking Russian general "will be is an embarrassment for Putin," says former MP and security analyst Tobias Ellwood.
Igor Kirillov, the head of Russia's nuclear, biological and chemical defence forces, was killed when a device hidden in a scooter was detonated, according to the Russian TASS news agency.
Ukraine's intelligence service said that Kirillov was responsible for "the massive use of banned chemical weapons" against the Ukrainian military.