Reports from the restive Russian North Caucasus republic of Daghestan say at least two police officers were injured when a military convoy accompanied by police came under fire as it passed through the town of Khasavyurt.
Security officials say an operation has been launched to apprehend the attackers.
The incident was reported following a violent weekend in Russia's Caucasus republics.
A suicide bombing at a funeral in neighboring Ingushetia on August 19 killed eight policemen.
Ingushetia has declared a three-day period of mourning for those victims.
On August 18, masked gunmen attacked worshippers at a Shi'ite mosque in Daghestan, wounding eight people.
Violence involving Islamic militants and security forces in Russia's North Caucasus -- which includes Daghestan, Chechnya, and Ingushetia -- causes hundreds of deaths and injuries each year.
Based on reporting by Interfax and ITAR-TASS