Russia awarded medals to five nuclear experts it described as "national heroes" who died in a mysterious explosion at sea while testing a rocket engine that caused a high level of radioactivity, while the city of Sarov, which includes the main base of nuclear research in Russia, mourned them.
The TASS news agency quoted officials as saying that the fire caught fire in the missile; causing the explosion, and the force of the explosion to throw several people at sea.
Officials provided very scant information about the explosion on a White Sea platform off northern Russia, which led to a high level of radiation in a nearby city.
Nuclear experts in the United States said they suspected the blast occurred during a test of a cruise missile capable of carrying nuclear warheads that Russian President Vladimir Putin boasted last year.
"Those who tested were national heroes," said Valentin Kostyukov, who heads a nuclear center that is part of Russia's state-owned nuclear company Ros-Atom.
"These people were the elite of the Russian Federal Nuclear Center and conducted the test under incredibly difficult conditions," the spokesman said.
The five experts, who work at the center in the closed city of Sarov, about 500 km (500 miles) east of Moscow, will be awarded national medals, Kostyukov said. The municipality of Sarov declared two days of mourning, flag flags were defeated and recreational activities were canceled, and experts said that the experts died while “performing a mission of national importance”.
Although the Defense Ministry initially said there was no change in the radiation level, authorities in the nearby city of Severodvinsk spoke of what it described as a brief increase in the radiation level, without giving an explanation.
Local residents have stored iodine, which is used to reduce the impact of radiation exposure after the incident, local media reported.
During the Cold War, the city of Sarov was a center of secret research, known as Arzamas-16, where the first Soviet nuclear weapons were made.