Edward Snowden has received a Russian passport after swearing an oath of allegiance to the country that has sheltered him from US authorities since 2013, his lawyer has said. Snowden, 39, a former intelligence contractor who leaked secret files that were reported on by the Guardian, was granted Russian citizenship in an order signed by Vladimir Putin in September. On Friday, Snowden’s lawyer, Anatoly Kucherena, said Snowden had received his passport. “He took the oath,” he said. The decision has come at an extremely inauspicious moment, after Russia’s invasion of Ukraine and subsequent descent into international isolation. Russia has mobilised its population for war and threatened to use nuclear weapons in order to defend territory it has occupied in Ukraine. Kucherena said on Friday that Snowden was “happy” and that Russian citizenship would prevent him from being extradited. “He of course is happy and thankful to the Russian Federation for his citizenship – he’s now a fully fledged citizen of Russia,” Kucherena said. “And most importantly, under the Russian constitution, he cannot be given up to a foreign state.” Kucherena could not immediately be reached for further comment. No photographs or video of the ceremony have been released. In Washington, state department spokesman Ned Price said the US was aware of reports that Snowden had finalised his Russian citizenship and said the Biden administration would not be surprised if the reports were correct. “Mr Snowden has long signalled his allegiance to Russia. This step would only formalise that,” Price told reporters. Individuals receiving Russian citizenship are required by law to pledge to “observe the constitution and legislation of the Russian Federation, the rights and freedoms of its citizens, to fulfil the duties of a citizen of the Russian Federation for the benefit of the state and society, to protect the freedom and independence of the Russian Federation, to be loyal to Russia, [and] to respect its culture, history and traditions”. Snowden’s wife, Lindsay Mills, is also said to be applying for Russian citizenship. They live at an undisclosed location in the country with their two sons, who were born in Russia. Snowden wrote in September: “After years of separation from our parents, my wife and I have no desire to be separated from our sons. After two years of waiting and nearly 10 years of exile, a little stability will make a difference for my family. I pray for privacy for them – and for us all.”