A former commander with the Russian mercenary Wagner Group has sought asylum in Norway after deserting the organisation that has played a central role in some of the major battles of the Ukraine conflict.

Andrey Medvedev, 26, crossed the border into Norway near the Pasvikdalen valley shortly before 2am last Friday, where he was arrested and detained by border guards.

The Norwegian Directorate of Immigration (UDI) confirmed to the Associated Press that Andrey Medvedev sought shelter in the country but “for reasons of security and privacy … cannot comment further on this matter”.

Police, who did not confirm his identity, said in a statement to Agence France-Presse that a man was “detained by Norwegian border guards and Norwegian police at 1.58am (0058 GMT)” on Friday morning.

“He has applied for asylum in Norway,” said Tarjei Sirma-Tellefsen, chief of staff for the police in Finnmark, northern Norway.

Medvedev’s Norwegian lawyer, Brynjulf Risnes, told the BBC that Medvedev was being held in Oslo where he faces charges of illegally entering the country and that he deserted after witnessing war crimes in Ukraine.

Risnes said his client was no longer in custody, but at a “safe place” while his case was being analysed. “If he gets asylum in Norway that accusation [of illegal entry] will be dropped automatically,” Risnes said.

“He has declared that he is willing to speak about his experiences in the Wagner Group to people who are investigating war crimes,” the lawyer said, adding that Medvedev alleged he had served as a unit commander in charge of between five and 10 soldiers.

Norwegian police said they were notified late on Thursday by Russian border guards who discovered traces in the snow that could indicate that someone had crossed the border illegally. The man was detained by border guards and the arrest was undramatic, police said.

Medvedev’s lawyer told AFP on Monday that after crossing the border his client had sought out locals and asked that they call the police.

Medvedev has been on the run since he defected from the Wagner Group on 6 July, according to Norwegian news agency NTB.

He told a Russian human rights group that he was ready to tell everything he knows about the Wagner Group, its activities and its founder, Yevgeny Prigozhin, a millionaire with ties to Russian president Vladimir Putin. Prigozhin confirmed to the BBC that Medvedev was a former Wagner soldier.

In an interview with the Gulagu.net rights group, Medvedev said he grew disaffected after his contract was repeatedly extended by Wagner without his consent and witnessing the killing and mistreatment of Russian prisoners who were brought to the front by Wagner.

Medvedev said losses were very high after Wagner began sending large numbers of prisoners to the front in the second half of 2022. Wagner’s internal security service handed out extreme punishment, Medvedev said.

He said a man who was shown in November being executed with a sledgehammer had been part of his unit.

Prigozhin’s statement did not address Medvedev’s accounts of punishment and of battlefield losses, or that his contract was repeatedly extended.

Gulagu.net also published an interview with Medvedev, where he detailed his dramatic escape. “When I was on the ice [at the border], I heard dogs barking, I turned around, I saw people with torches, about 150 metres (500ft) away, running in my direction,” Medvedev says in one video. “I heard two shots, the bullets whizzed by.”

According to Risnes, Medvedev said “he experienced something completely different from what he was expecting” after joining the private mercenary group, which has been at the forefront of key battles in Ukraine.

Wanting to leave and after claiming he witnessed war crimes in Ukraine, Medvedev said his contract was extended without his consent. “He understood that there was no easy way out, so that’s when he decided to just run,” Risnes said.

Medvedev then reportedly spent two months underground in Russia, before crossing the border into Norway last week.

The Guardian has not been able to independently verify Medvedev’s account.

The Wagner Group includes a large number of convicts recruited in Russian prisons who have spearheaded attacks in Ukraine. The group has become increasingly influential in Africa, where it has been pushing Russian disinformation, building alliances with regimes and gaining access to oil, gas, gold, diamonds and valuable minerals.

The Associated Press and Agence France-Presse contributed to this report