Russia’s top security agency says it has arrested four Russians accused of making preparations to kill senior Defense Ministry officials on Ukraine's orders.

Lieutenant General Igor Kirillov, head of Russia’s Nuclear, Biological, Chemical Defence Forces (NBC), was killed in an explosion in Moscow in an assassination claimed by Ukraine

The Federal Security Service of Russia said a series of assassination attempts had been foiled. Four Russian citizens have been arrested.

Russia’s Federal Security Service (FSB) said it thwarted multiple assassination plots allegedly orchestrated by Ukrainian intelligence and carried out by Russian citizens recruited to execute the attacks,