Ukraine’s SBU security service alleged Thursday that a commander of the Russian Volunteer Corps, a unit of far-right Russians fighting alongside Ukrainian forces, was recruited by Moscow to assassinate a Russian opposition figure.

The alleged plot comes as questions remain over the disappearance of Russian Volunteer Corps deputy commander Stepan Kaplunov.

Ukrainian law enforcement authorities said Wednesday that they foiled an alleged plot by Russia’s FSB security service to assassinate an anti-Kremlin “opposition leader” in the…