Russian's state nuclear company says five people were killed in Thursday's rocket explosion on a naval test range.
A statement from Rosatom said three people were also injured in the incident.
They say the staff members suffered serious burns in the accident, which has been shrouded by mystery.
On Friday Russian government sources said two people died and six were injured in the Nyonoksa blast.

US carrying out rescue effort after losing aircraft in Iraq
Suspect shot dead after crashing truck into Detroit-area synagogue
Iran's supreme leader, in first remarks, vows to keep strait closed
FBI investigating fatal Virginia university shooting as act of terrorism
Four Bahrainis arrested for spying for Iranian Guard
Two US sailors injured after non-combat fire aboard carrier in Red Sea
First train to Pyongyang in six years leaves Beijing as neighbours revive link
Six vessels attacked in Gulf, Strait of Hormuz
