The Russian state security service says it has detained seven members of the Islamic State (IS) group in the Urals city of Yekaterinburg.
The FSB says the seven, who include citizens of Russia and Central Asian states, were detained on February 7.
It says the group was planning to carry out "high-profile terrorist attacks using self-made explosive devices on the territory of Moscow, St. Petersburg, and the Sverdlovsk region" in the Urals.
The FSB says a laboratory for making explosive devices was uncovered during the search operation.
The group was led by a member of the IS group who had come to Russia from Turkey, it adds, and the alleged militants planned to join IS fighters in Syria after perpetrating the attacks in Russia.
Russian authorities estimate that some 3,000 Russian citizens have joined the IS group in Syria.