The device exploded outside the home of Boris Chochiev, the head of the presidential administration in South Ossetia, RIA Novosti reported.
The house sustained minor damage.
South Ossetia President Leonid Tibilov called for an emergency meeting of the security council to investigate the incident.
Authorities said they were searching for the attackers.
In 2008, Russia went to war with Georgia, a former Soviet state, over South Ossetia and Abkhazia. Russia and a few other nations recognize their independence, but the two regions remain in dispute.