Moscow under fire for illegally holding Ukrainians
Ukraine's foreign affairs ministry is lodging a protest with Russia.
The complaint concerns an attack on a Ukrainian official.
In the Russian city of Grozny, where two Ukrainian political prisoners are on trial, a group of men attacked a Russian human rights activist.
Ukrainian consul Oleksandr Kovtun, who was standing nearby, was also caught up in the assault.
Ukraine's foreign ministry is expressing its protest at the incident and says it condemns Russian attempts to intimidate those who speak out about human rights violations.