Russian Federation has said that five nuclear agency staff were killed by a blast during testing of a nuclear-powered missile at an Arctic military facility on Thursday.
Rosatom said the accident occurred during tests on a liquid propellant rocket engine on Thursday, RIA reported.
"Searches continued as long as there was hope to find survivors", Interfax news agency cited Rosatom as saying.
Rosatom said its staff were providing engineering and technical support for the "isotope power source" of a missile being tested. Authorities said the port has been closed off after the incident.
Putin said in February that tests on the Burevestnik were going successfully. An expert from Moscow's Institute for Nuclear Research, Boris Zhuikov, told RBK independent news site that isotope power sources are mainly used in spacecraft and are not usually unsafe for people working with them.
The defence ministry initially said no change in radiation was detected, but that was contradicted by local officials in the nearby city of Severodvinsk who said radiation had briefly spiked, without saying how high.
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The authorities have released few details of the accident at the Nyonoksa test site on the White Sea, used for testing missiles deployed in nuclear submarines and ships since the Soviet era.
It caused a radiation spike around the military testing site in the Arkhangelsk region that drove radiation levels up to 20 times the normal level in the nearby city of Severodvinsk for about half an hour.
Russia's military in an initial statement said two were killed in the accident and it was not known whether those two deaths were among the five that Rosatom reported.
"I think the radioactive contamination was fairly weak and the consequences will be [felt by] the people who were at the scene of the incident itself". Russian Federation maintains a veil of secrecy around its military installations in the region, near where its northern fleet, including nuclear submarines, are stationed.
Local residents have been stocking up on iodine, used to reduce the effects of radiation exposure, after the accident, regional media have reported.
"People started to panic". Five nuclear scientists were killed in this accident, while nine were injured.
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