Russia's FSB said the suspects were militants of a banned radical Islamist group.
Russian security services have arrested 19 suspected militants of a radical Islamist group, accusing them of preparing attacks in the North Caucasus.
The Federal Security Service (FSB) announced the arrests on Monday after carrying out searches at "their places of residence and secret gatherings".
A machine gun, an automatic rifle, and over 40 copies of extremist materials were seized by the authorities.
An improvised explosive device containing more than 3 kilograms of TNT was also found in a nearby forest area as part of the searches.
Those detained are believed to be members of the Takfir wal-Hijra (Anathema and Exile) group, which has been banned in Russia since 2010.
The nineteen suspects were detained inKarachayevo-Cherkessia, the Krasnodar region, the Rostov region, and Crimea, the Ukrainian peninsula annexed by Russia in 2014, according to an FSB statement.
They have been accused of "promoting ideology and recruiting new supporters" and "planning to commit sabotage and terrorist acts".
The Russian Caucasus was shaken by two deadly conflicts in the 1990s and 2000s between federal forces and the Chechen separatist rebellion, which eventually pledged allegiance to the Islamic State group in June 2015.
The area has been plagued by militant attacks on security officials, but armed groups are much less active than in previous years.
"We will continue to take measures to identify and suppress the activities of extremist organisations," the FSB stated.