US intelligence officials are investigating a mysterious explosion that released radiation off the northern coast of Russian last week.
The New York Times reports the blast occurred during the test of a new type of nuclear-propelled cruise missile.
The US government has said nothing publicly about the detonation on Aug. 8, which could be one of the worst nuclear accidents since Chernobyl. Russia's Defense Ministry said a rocket engine exploded and at least seven people were killed in the accident, including scientists. Some Russian news reports cited unidentified sources who said up to 15 people were injured.
The latest accident happened offshore at a military shooting range in Nyonoksa in the northwestern Arkhangelsk region, causing a fire.
A Russian Navy facility is also located on the island that serves as a base for testing intercontinental ballistic missiles intended for nuclear submarines.
The ministry claimed there was no release of radioactivity or any toxic substances, but a local official in Severodvinsk, 19 miles east of Nyonoksa, reported a spike in radiation. Russian news media later reported radiation briefly rose to 200 times normal background levels.
Emergency officials issued a warning to all workers to stay indoors but authorities insisted that the city's residents never were in any danger.
Over the weekend, administrators at a research facility that had employed five of the scientists who were killed confirmed a small nuclear reactor had exploded during an experiment, according to The Times.
US intelligence officials believe the explosion was from a prototype of a cruise missile NATO has named SSC-X-9 Skyfall. Russian President Vladimir Putin has flaunted the cruise missile, saying it can reach any corner of the world because it is powered by a small nuclear reactor and not by a liquid propellant which has distance limitations.
Putin boasted in 2018 that the Skyfall missile could successfully evade American missile defense systems. When the missile is launched it flies at low altitudes on an unpredictable course, according to released Pentagon reports.
However, many military experts have long regarded Putin's efforts as part fantasy, using technology that the US first tried and failed to master in the 1950s and 1960s.
But some think Putin will continue experimenting until his dream is fulfilled, returning Russia to the same status of a superpower as it was as the former Soviet Union.
"Some believe the failed test involved a 'doomsday' nuclear-armed cruise missile theoretically of unlimited range due to what the Russians call its 'atomic battery.' It is only capable of flying indefinitely, of course, if that power plant actually works," Frank Gaffney, executive chairman of the Center for Security Policy, said Monday on his "Secure Freedom Minute" radio broadcast.
"But, this incident appears to be just the latest in a series of failed tests of this weapon system, which NATO calls the 'Skyfall,' with accompanying releases of radioactive material," Gaffney continued.
"The trouble, of course, is not simply Vladimir Putin's evident disregard for the safety of these missiles and the environmental hazards posed by their further development. It is his determination recklessly to pursue ever-more dangerous weapons of mass destruction with which to threaten, and perhaps annihilate us," he concluded.