The authorities in Severodvinsk, a city around 30 kilometres (19 miles) away from the test site, said on their website that automatic radiation detection sensors in the city "recorded a brief rise in radiation levels" on Thursday morning, without saying what the levels were.
The Nyonoksa site carries out tests for virtually every missile system used by the Russian navy, including sea-launched intercontinental ballistic missiles, cruise missiles and anti-aircraft missiles.
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The military had not previously described the accident as involving nuclear fuel and said radiation levels were normal afterwards.
Citing data from the Emergency Situations Ministry, Greenpeace said radiation levels had risen 20 times above the normal level in the city. That would not explain the radiation surge, although liquid fuel for rockets can also be highly toxic. In March past year, he held a briefing on the country's latest nuclear-powered cruise missile.
On Monday, one person was killed and eight others were injured in a blaze at an ammunition dump in Siberia.
The region's governor said there was no need to evacuate residents, RIA said.
Five specialists from the Russian federal nuclear center in Sarov (Nizhny Novgorod region) killed following a rocket explosion at a naval test range outside the city of Severodvinsk, will be recommended for state awards, center's Director Valentin Kostyukov said in a speech on local television.
No risky substances were released into the atmosphere, the government organisation said.