Kirillov and his assistant died after an explosive device, which was planted in an electronic scooter that was parked outside his apartment, went off.

Lt Gen Igor Kirillov was reportedly present outside the apartment when the blast occurred.

As per Sputnik news agency report, the detained person was recruited by the Ukrainian special services.

"As a result of operational and investigative activities conducted jointly with the Russian Ministry of Internal Affairs and the Russian Investigative Committee, the Russian Federal Security Service has identified and detained a citizen of Uzbekistan, born in 1995, who detonated a homemade explosive device near a residential building on Ryazanskiy Prospekt in Moscow, which resulted in the death of ... Lieutenant General Igor Kirillov, born in 1970, and his assistant, Major I.V. Polikarpov, born in 1983," the  Russia's Federal Security Service said in a statement as quoted by Sputnik.

Ukraine's security service had already claimed it was behind the killing, a source told the BBC

Kirillov is one of the senior-most Russian military officials who was assassinated in  Moscow since the conflict with Ukraine began.

A source in Ukraine's SBU security service told BBC that Kirillov was "a legitimate target" and alleged he had carried out war crimes.

Fighting has been going on since Russia launched a full-scale invasion in 2022.