Russia has arrested four people on suspicion of plotting to assassinate senior defence officials and their families on Ukraine’s orders, the Kremlin’s Federal Security Service (FSB) said.

Russia’s top security agency says that it has arrested several suspects accused of involvement in an alleged Ukrainian plot to assassinate senior military officers.

Igor Kirillov, head of Russia's nuclear and chemical defense, helped spread false claims about Ukraine, the U.S. and COVID-19.

Russia's security service said four Russian citizens were recruited by Ukraine to carry out the assassinations

The head of Russia's chemical and biological forces, Lt. General Igor Kirillov, was killed in a Moscow bomb blast claimed by Ukraine.

Kirillov ran Russia’s nuclear, biological and chemical defense forces. Kyiv previously accused him of ordering the use of chemical weapons against Ukraine.

Kirillov, who has been killed in Moscow, was accused by the West of overseeing the use of chemical weapons on the battlefield in Ukraine.

It is believed that the bomb was hidden in or on an electric scooter at the location, which emergency teams were seen examining.

Igor Kirillov, a senior general in charge of Russia’s nuclear defence forces, was killed on Tuesday in a bomb blast in Moscow. A source in the Security Service of Ukraine (SBU), talking to Al Jazeera,

Russia said on Wednesday it had detained an Uzbek man who had confessed to planting and detonating a bomb which killed a top general, Igor Kirillov, in Moscow on the instructions of Ukraine's SBU security service.

Lieutenant General Igor Kirillov was the head of Russia's Nuclear, Biological, and Chemical Protection Troops. Authorities said the explosion was caused by a bomb hidden inside an electric scooter.

Lt. Gen. Igor Kirillov was killed Tuesday by a bomb hidden on an electric scooter outside his apartment building.