Unidentified gunmen attacked a car carrying investigators in Russia's North Caucasus republic of Ingushetia late Friday, police said.
The attack, in which two people were injured, took place at around 11.30 pm Moscow time (2030 GMT) in Nazran city.
Russia has launched operations against militants in the North Caucasus republics, especially Ingushetia, Chechnya and Dagestan. These regions have seen an upsurge of militant violence lately, with frequent attacks on police and government officials.
President Dmitry Medvedev has described the situation in the region as a major threat to national security.