As a result of the attack, a BMW off-road vehicle lost control and crashed into another car. The incident took place in front of the regional department of the Federal Penitentiary Service.
The source told RIA Novosti that gunmen fired with assault rifles from a car, which was subsequently found burnt out on the city outskirts.
The attack came a day after the assassination of the mayor of Vladikavkaz. Vitaly Karayev was shot while getting into his car outside his home.
The Kataib al-Khoul Islamist group claimed responsibility for the mayor's murder, in a statement on Thursday released by a website believed to have links to Chechen militants.
North Ossetia was the focus of international attention in September 2004, when terrorists seized Beslan's School No.1 killing 331 people including 186 children. The republic neighbors the troubled Chechnya and Georgia, with which Russia fought a brief war in August.