Unknown suspects cast a grenade at a police patrol on early Sunday in the city of Kaspiisk, in the Russian North Caucasus republic of Dagestan, a local police spokesman said, RIA Novosti reported.
"Unknown suspects cast a grenade at policemen from a car they were riding and fled the scene. None of the policemen were injured," he said.
The spokesman did not specify whether the grenade exploded or not, adding that the suspects were not detained.
Sporadic terrorist attacks and militant clashes are common in Russia's largely Muslim North Caucasus republics, especially Dagestan, Chechnya and Ingushetia.
The Kremlin has pledged to wage "a ruthless fight" against militant groups but also acknowledged a need to tackle unemployment, organized crime, clan rivalry and corruption as causes of the ongoing violence in the region.