A former commander of the Russian armed group Wagner requested asylum in Norway after defecting from the mercenary group.
And Andrey Medvedev, 26, crossed the border into Norway last Friday, where he was detained by border guards.
His lawyer, Brynjolf Resens, told the BBC he was currently being held in the Oslo region, where he faces charges of illegal entry to Norway.
Resnes said his client left Wagner after witnessing war crimes in Ukraine.
Norwegian Border Guard confirmed to the BBC that a Russian man had been arrested after crossing the country’s 198-kilometre border with Russia, but said he could not comment further for “security and privacy reasons”.
Tarje Sirma-Televesen, chief of police staff in the Norwegian region of Finnmark, said a man had been detained by border patrol and said he had applied for asylum.
But the Russian human rights organization Gulago, which helped Medvedev leave Russia, has confirmed his identity. His escape is believed to be the first known example of a group’s soldier defecting to the West.
Vladimir Ussishkin, the founder of Gulagaw, told the BBC that Medvedev joined the paramilitary group in July 2022 on a four-month contract, but left after witnessing a range of human rights abuses and war crimes while serving in Ukraine.
He said Medvedev is a former soldier in the Russian army and that he later served time in prison between 2017 and 2018 before joining the Wagner Group.
Usichkin said he was put in charge of the Wagner Division in Ukraine, where the mercenary group supplied him with about 30-40 soldiers each week.
In a video clip Gulago posted on its social media channels, Medvedev said he fled Ukraine in November after being informed that the group intended to extend his contract indefinitely.
After spending two months in hiding in Russia, he crossed into Norway last week.
Resnes said his client also witnessed a range of war crimes while fighting in Ukraine, including witnessing “executions of deserters” by the Wagner Group’s internal security service.
“In short, he felt betrayed and wanted to leave as soon as possible,” Resnes said.
He added that he believed Medvedev had taken some evidence of war crimes with him to Norway and that he planned to share his information with groups investigating war crimes in the coming weeks.
Responding to the allegations, the founder of the Wagner Group, Yevgeny Prigozhin, confirmed that Medvedev was a former Wagner soldier.
But he said in a press statement that Medvedev holds Norwegian citizenship and commanded a battalion of soldiers from the Scandinavian country.
Prigozhin also accused him of “mistreating prisoners” and said his former employee was “extremely dangerous”. Resnes told the BBC that Prigozhin’s allegations were not true.
British officials believe the Wagner Group makes up around 10% of Russian forces in Ukraine, and played a significant role in helping Russian forces take the town of Solidar in the eastern Donbass region last week.
Thousands of its troops were recruited from Russian prisons. Prigozhin, himself an ex-convict, promised the recruits his release in return for six months of service in Ukraine.
And before the invasion of Ukraine, Wagner had only a few thousand mercenaries. It is believed that most of them were experienced former soldiers, including some of Russia’s elite regiments and special forces.
It is believed that Wagner has deployed forces to Syria, Libya, Mali and the Central African Republic since 2015.