Investigators are conducting a criminal investigation into murder, terrorist acts, and the illegal circulation of weapons and ammunition "in connection with the death of two servicemen in the capital," the committee said in a statement.

Earlier in the day, Lieutenant General Igor Kirillov, head of the Russian Armed Forces’ radiological, chemical and biological defense troops, and his assistant were killed by an explosion in a residential building in Moscow.

The committee had previously said it opened a criminal case, adding the blast occurred after the detonation of an explosive device planted in a scooter parked next to the entrance of the residential building.

Lieutenant General Igor Kirillov, head of the Russian Armed Forces' radiological, chemical and biological defense troops was killed by an explosion in a residential building in Moscow.