Russian opposition leader Alexei Navalny has said that one of his allies had been forcibly conscripted and sent to serve at a remote Arctic base, in a move his supporters said amounted to kidnapping.

Ruslan Shaveddinov, a project manager at Navalny’s anti-corruption foundation, went missing Monday after police broke into his Moscow flat and his phone’s SIM card was disabled.

He resurfaced Tuesday at a secret air defence base on the remote Novaya Zemlya archipelago in the Arctic Ocean, Navalny said.

Separating the Barents and Kara seas, the Novaya Zemlya islands were used by the Soviet Union to conduct nuclear tests.

“He has been unlawfully deprived of freedom,” said Navalny, president Vladimir Putin’s top opponent, in a blog post, calling the 23-year-old a “political prisoner”.

The Russian military insisted that Shaveddinov had been dodging the draft for a long time.

Russian men are eligible for conscription between the ages of 18 and 27 and serve one year’s military service. However, many find ways to avoid this in a corrupt, flawed system.

Opposition supporters called for Shaveddinov’s release, staging protests in Moscow including outside army headquarters.

“Happy New Year 1937”, said one placard, referring to the peak year of Stalin-era purges. “Ruslan Shaveddinov has been kidnapped by the FSB (security service) and exiled to Novaya Zemlya,” said the sign, according to photographs released by Navalny’s allies.

A man holds a poster reading ‘Happy New Year 1937, Ruslan Shaveddinov has been kidnapped by the FSB (security service) and exiled to Novaya Zemlya’ during a protest in central Moscow. Photograph: Dimitar Dilkoff/AFP via Getty Images

Navalny said Shaveddinov has a medical condition that disqualifies him for military service but that he was forcibly drafted and sent to the Arctic base without basic training.

Vyacheslav Gimadi, a lawyer for Navalny’s foundation, said defence minister Sergei Shoigu and commander-in-chief Putin were directly responsible for what he claimed was an act of “kidnapping”.

Navalny’s spokeswoman Kira Yarmysh, who is Shaveddinov’s partner, said Shaveddinov had recently acted as a contact person for opposition lawmakers in Moscow city parliament.

“Perhaps this is the reason this has happened,” Yarmysh told AFP.

She said Shaveddinov had managed to call her from Novaya Zemlya using other people’s phones.

Putin’s spokesman Dmitry Peskov told reporters he did not know whether Shaveddinov had been dodging the draft.

“If he had and was drafted in this manner then everything was done in strict accordance with the law.”

But prominent rights campaigner Valentina Melnikova told AFP it was unusual for the authorities to send conscripts to remote Arctic outposts known for harsh weather conditions and long polar nights.

Authorities have been steadily ramping up pressure on Navalny and his allies in recent years.