The man, who is in his early-thirties, was detained in the city of Khasavurt, the spokesman said, adding that the suspect had intended to "get into a group of policemen while wearing a grenade belt and TNT packs."
He also added that a search of the suspect's house had been performed early on Friday, and had revealed three grenades, TNT, and "extremist literature".
Parliamentary elections are due in Russia on December 2, and Russian authorities have been warning of possible terrorist attacks in the lead-up to the polls.
A bomb on a bus in the southern Russia city of Togliatti killed eight people and left 50 injured on October 31, and on November 22 another explosion ripped through a bus in the Russian Republic of North Ossetia, killing four.
No group has claimed responsibility for either of the blasts.
