Three other members of the Russian nuclear agency Rosatom were injured in the blast.

The Russian nuclear agency Rosatom announced on Saturday that five members of its staff had been killed in the explosion on a missile launch base in Russia's Far North, thus adding to the army's initial estimate of two deaths.

In a statement, Rosatom said the accident also injured three other members of staff including burns. Rosatom adds that its staff provided engineering and technical support for the "isotopic energy source" of the missile engine.