The Russian business news outlet RBK said Lankov confirmed to the outlet he was detained by Latvian police during a lecture on North Korea and placed on a blacklist by the country's authorities.
He later said he was turned over to immigration services. The reason for his detention was not immediately clear. Russia's Tass news agency also reported his detention.
About 11pm on Tuesday Moscow time, Lankov told RBK he was still being held, adding that lawyers were working on his case and friends were helping with logistics.
Officials at South Korea's Kookmin University, where Lankov is a professor of history, said they were trying to assess the situation. A text message sent to Lankov's phone was not immediately returned.
A native of Leningrad, now called St Petersburg, Lankov lived for years in North Korea as an exchange student in the 1980s and has studied the country throughout his career.
In the 1990s, he worked in South Korea and Australia, at the Australian National University, and since 2004 has taught in Seoul. He holds dual Russian and Australian citizenship.
Lankov has been known for his cool, realist view of North Korea, which he often describes as a Machiavellian regime squeezing limited resources and manipulating major powers to ensure its survival.
He has also expressed critical views of Russia's war in Ukraine and Moscow's use of North Korean troops to sustain its campaign.
In April 2025, a court in Moscow reportedly fined him 10,000 rubles ($A184) for taking part in the activities of an organisation that had been recognised as "undesirable" in Russia.
Lankov told RBK at the time he learned about the case from journalists.
