This followed another explosion at a Siberian army facility on August 5.
The state nuclear company said five staff members were killed on Thursday when there was a blast at the Nyonoska Navy facility in Russia's northwest.
Radiation levels spiked by up to 16 times in the nearby city of Severodvinsk.
The Russian government reveals more on the nuclear missile test explosion.
Al Jazeera's Step Vaessen reports from Moscow.
Al Jazeera's meteorologist Jennny Harrison explains.
