Russian security service claims of detaining a 29-year-old Uzbek man has been detained over the killing of senior general Igor Kirillov and his assistant in Moscow, reports BBC.
The Russian security service said the suspect was recruited by Ukrainian intelligence, according to state media agencies.
A Ukrainian source told the BBC on Tuesday that the killing was orchestrated by Ukraine's security service.
The Ukrainian security source said Kirillov - who was Russia's chemical weapons chief - was "a legitimate target" and alleged he had carried out war crimes.
On Monday, the day before the killing, Ukraine charged Kirillov, 54, in absentia, saying he was "responsible for the mass use of banned chemical weapons".
The Russian Federal Security Service's (FSB) public relations centre said on Wednesday the detained 29-year-old was "suspected of committing a terrorist attack".
A statement said that during "interrogation he explained that he was recruited by the Ukrainian special services".
The FSB said the suspect had been "guaranteed" a reward of $100,000 and permission to move to the European Union in exchange for killing Kirillov.
It added that on Ukraine's instructions, he arrived in Moscow and rented a car to monitor Kirillov's residence.
The FSB said: “He placed the explosive device on an electric scooter, which he parked at the entrance to the residential building where Kirillov lived.”
He also installed a camera live-streaming a video feed from the site to his handlers in the Ukrainian city of Dnipro.
When they saw Kirillov emerge from the house, the suspect detonated the bomb, the statement furthered.
However, Lt Gen Igor Kirillov, head of the Nuclear, Biological, Chemical Defence Forces (NBC), was outside a residential block early on Tuesday when an explosive device hidden in a scooter was detonated remotely.
Bd-Pratidin English/ Afsar Munna
