A Russian lieutenant general and his assistant were killed by an explosion in a Moscow residential building on Tuesday morning.
Lieutenant General Igor Kirillov, head of the Russian Armed Forces' radiological, chemical and biological defense troops, was killed in the explosion, said the Russian Investigative Committee.
Preliminary information indicated that the explosion occurred following the detonation of an explosive device with an equivalent power of approximately 1 kilogram of TNT, according to law enforcement agencies quoted by TASS on Tuesday.
The explosive device was planted in a scooter, said the committee, adding that a criminal case has been opened in connection with the killing.
The Ukrainian military announced on Tuesday that the attack on Kirillov was a special operation carried out by the Security Service of Ukraine.
A day earlier, the Security Service of Ukraine had accused Kirillov of deploying banned chemical weapons against Ukrainian forces, labeling him a war criminal.
Russian Foreign Ministry's spokesperson Maria Zakharova said on social media that Kirillov had devoted himself to exposing a series of biological laboratory activities carried out by the United States in Ukraine.
Dmitry Medvedev, deputy chairman of the Russian Security Council, said that Ukraine's attempt to intimidate the Russian people is doomed to failure and will inevitably lead to retaliation against Ukraine's top military and political leadership.