AP reported that on December 18, Russia's intelligence agency said that the suspect involved in the assassination of Lieutenant General Igor Kirillov in Moscow on December 17 had been arrested.
The suspect was described as an Uzbek citizen who had been recruited by Ukrainian intelligence services.
The Russian Federal Security Service (FSB) did not disclose the name but said the suspect was born in 1995.
According to a press release from the FSB, the suspect claimed that he had been recruited by Ukrainian special services.
Lieutenant General Igor Kirillov was assassinated on December 17 by a bomb hidden in a scooter outside his Moscow apartment building.
The bomb used in the attack was detonated remotely. Images at the scene showed broken windows and charred brick walls.
The Russian Investigative Committee said it is investigating Kirillov's death as a terrorist attack and Moscow officials have pledged to punish Ukraine.
The incident came a day after the Security Service of Ukraine (SBU) brought criminal charges against him for using banned chemical weapons.
A Ukrainian official said that SBU carried out the attack.
Previously, Mr. Kirillov (54 years old) was sanctioned by a number of countries, including the UK and Canada, for his actions in Russia's military campaign in Ukraine.
However, Russia has denied the use of chemical weapons in Ukraine and, in turn, accused Kiev of using toxic substances in combat.
Lieutenant General Igor Kirillov - commander of the Russian Radio, Chemical and Biological Defense Forces since 2017 - was one of the prominent figures in making accusations about Kiev's use of toxic substances in combat.
He has held many press conferences to accuse the Ukrainian army of using toxic substances and planning to launch radioactive attacks.
However, the allegations were denied by Ukraine and its Western allies, arguing that it was just propaganda.
