Two people have been killed in an explosion at a naval test facility in northern Russia, officials say.The victims were civilian specialists. At least four others - both military and civilian personnel - were injured.The facility, in the north-western Arkhangelsk region in the Russian Arctic, has not been named.The blast occurred during testing of a rocket engine, officials said, adding that the explosion did not release harmful materials or radiation."During testing of a liquid jet engine an explosion and combustion of the product occurred," a statement by the defence ministry carried by Russian news agency Interfax said."There have been no harmful chemicals released into the atmosphere, the radiation levels are normal," it added.Emergency aircraft were used to airlift the injured. They included defence ministry officials and developer company representatives, who "had injuries of varying severity", the statement added.There had been earlier reports of a fire at a military facility near the town of Nyonoksa in the same region, which hosts a navy missile test range known to be used for testing intercontinental ballistic missiles, or ICBMs.The Nyonoksa naval test range carries out tests for virtually every missile system used by the Russian navy, including sea-launched ICBMs, cruise missiles and anti-aircraft missiles.Earlier, residents of Nyonoksa reported a fire in the village and explosions nearby.It is the second accident involving Russia's military this week.On Tuesday, one person was killed and eight others were injured in a blaze at an ammunition dump in Siberia.Flying munitions damaged a school and a kindergarten in the area. More than 9,500 people were evacuated.An investigation is under way into the cause of the incident.