Russia's Foreign Ministry said the extradition of blogger Alexander Lapshin to Baku was against the "spirit" of relations between Russia and Belarus.
Azertac, Azerbaijan’s state news agency, has written that Lapshin, who holds Russian and Israeli citizenship, went to the occupied Karabakh region of the country -- currently under illegal Armenian control -- in 2012.
Baku issued an arrest warrant for Lapshin over his unauthorized travel and blog posts on the country’s territorial integrity.
Lapshin was detained in Belarus last December; the country’s Supreme Court approved his extradition to Azerbaijan on Tuesday.
Kremlin spokesman Dmitry Peskov told reporters on Wednesday Russia was doing "everything necessary" to protect Lapshin’s interests, reported the Interfax news agency.
Previously, Russian Foreign Ministry spokeswoman Maria Zakharova told a news conference it was “unacceptable” to extradite Russian citizens to third countries.