A group of unidentified assailants opened fire late on Monday on a unit of Russian borderguards stationed in Nazran, the largest city in the volatile North Caucasus republic of Ingushetia.
"At about 23.00 Moscow time (19.00 GMT), unidentified gunmen opened fire on borderguards in Nazran, using automatic weapons and a grenade launcher," a local police source told RIA Novosti.
"No casualties or damages to buildings have been reported so far," the source said.
Another police source said a group of investigators would inspect the site on Tuesday morning as it would be too dangerous to move around the area at night due to the possibility of another attack.
Russia's mainly Muslim North Caucasus republics, especially Chechnya, Dagestan and Ingushetia, have seen an upsurge of militant violence lately, with frequent attacks on police and officials.