Russian on Friday added two high-profile Kremlin critics to its list of "foreign agents: former chess champion Garry Kasparov and ex-tycoon Mikhail Khodorkovsky.
The infamous label, reminiscent of the "enemies of the people" of the Soviet period, is used extensively against opponents, journalists and human rights activists accused of conducting foreign-funded political activities.
Such "foreign agents" are subject to numerous constraints and laborious procedures, under pain of severe sanctions. In particular, they must indicate this status in all their publications.
In its updated website list, the Russian justice ministry said that Khodorkovsky, 58, and Kasparov, 59, have "sources" in Ukraine to finance their activities.
Soviet-born former world chess champion Kasparov is a longtime opponent of President Vladimir Putin and has lived in the United States for almost a decade.
Khodorkovsky was one of Russia's most powerful businessmen in the 1990s, before coming into conflict with the Kremlin when Putin came to power in 2000.
He spent ten years, from 2003 to 2013, in prison and then went into exile.
For years, he helped to finance the Russian opposition organisation Open Russia, which dissolved itself in May last year in the face of growing repression.
Since the start of Moscow's military operation in Ukraine on February 24, dozens of members of the Russian intellectual elite and journalists have left the country, as the authorities step up pressure against the last critical voices and media.