Daghestan's Interior Ministry says one policeman was killed and two people were injured in a drive-by shooting in the republic's capital Makhachkala on July 12.
The ministry said unidentified attackers opened fire on police at a checkpoint.
Two policemen were injured, one later died of his wounds in the hospital.
The driver of a vehicle police had stopped at the checkpoint was also injured.
The attack comes after a district court judge was shot dead in his car and bomb blasts injured two policemen and also derailed a cargo train over the weekend in the restive North Caucasus republic.
Russia is struggling to quash an Islamic insurgency in the North Caucasus, which also includes Chechnya and Ingushetia.
compiled from agency reports