The FSB said it had seized a suicide belt, homemade bombs and automatic weapons from the suspects this month.
"Besides spreading ideological propaganda and recruiting new followers, they were plotting acts of sabotage and terror attacks in the North Caucasus," the FSB said< DW reported.
The detainees are suspected members of the Takfir wal-Hijra extremist group, an organization which was founded in Egypt and has ties to al-Qaeda.
Ten out of the 19 arrested were organizers, and the rest were active participants, Russian news agency RIA said.
The members were spread across the Rostov, Krasnodar and Karachay-Cherkessia regions, as well as Crimea, the peninsula Moscow annexed from Ukraine in 2014.
Footage from the arrest showed FSB operatives climbing an apartment building and entering through a window to detain a suspect.
In November 2014, the FSB detained 14 members of the suspected members of the group under similar circumstances.
The group's targets include "civilians, media, mosques, journalists, political leaders, military, and Jews with assassination, armed assault, and bombings," according to trackingterrorism.org.
Russia has repeatedly been targeted by extremist militant groups, including in an attack on a train in a St. Petersburg metro tunnel in 2017. The North Caucasus have also faced similar attacks in recent years.
Russian authorities have announced several operations to snuff out suspected extremist cells, particularly in the south of the country and the Muslim-majority republic of Chechnya.