Moscow is surprised by the comments of the US State Department and US Embassy regarding an incident with the US diplomats in Severodvinsk, Russian Foreign Ministry said in a statement.
US diplomats were not detained in Severodvinsk, they got into car and have possibly already arrived in Moscow, the ministry added.
US embassy staffers try to get into restricted areas across Russia all the time, the Russian Foreign Ministry said.
Moscow will send a letter of protest to the United States over the incident involving three US diplomats removed from a train in Russia's Arkhangelsk region, according to Deputy Foreign Minister Evgeniy Ivanov.
He noted that the US officials were protected by diplomatic immunity, adding that an investigation would continue.
"The trip was coordinated, but Arkhangelsk was their destination, and they somehow found themselves near Severodvinsk, so, I believe, some administrative protocols will be prepared. I think a further investigation will be conducted," Ivanov said.
Three US diplomats from the US Embassy in Moscow were removed from a train travelling from Nenoksa to Severodvinsk on 14 October. Initial media reports claimed that the diplomats did not have papers allowing their presence on restricted territory. Meanwhile, US embassy's spokeswoman, Rebecca Ross, said that the diplomats had properly filed a travel notification with the Russian Defence Ministry.
The Russian Foreign Ministry confirmed on Wednesday that the US diplomats were on an official trip, but notified the Russian Defence Ministry only of their plans to visit Arkhangelsk.