The deadly explosion is the second within a week at a Russian military site. There are conflicting reports about a short-term spike in radiation around the base.
Russia's Defense Ministry said two people died and four others were injured in an explosion at a military base used to test missiles in the far north of the country.
The explosion occurred during a test of a liquid-propellant jet engine in the small town of Nyonoksa in the northwestern Arkhangelsk region. The site is used to test intercontinental ballistic missiles that are used on nuclear submarines.
Following the explosion, the Defense Ministry said there was no release of radioactivity or any toxic substances, but a nearby town reported otherwise.
Authorities in the town of Severodvinsk, located around 30 kilometers (19 miles) away from the naval facility, said they "recorded a brief rise in radiation levels."
They added that the levels have since "normalized."
The incident on Thursday is the second deadly explosion to hit the Russian military in less than a week.
On Monday, a fire at an ammunition depot in Siberia caused a massive explosion that killed at least one person and injured 13 more, forcing several thousand people to flee their homes in the Krasnoyarsk region.
rs, cw/rt (AFP, AP, dpa, Reuters)