Assia's Federal Security Service (FSB) announced late last week that seven suspected followers of the Islamic State of Iraq and Syria (ISIS) had been arrested for allegedly plotting an attack in St. Petersburg, The Associated Press reported.
The agency reportedly found and seized explosives and other weapons while searching apartments in the city.
Russian TV stations also aired footage of FSB agents detaining an individual who later confessed that he was ordered to build "homemade bombs rigged with shrapnel," the AP reported.
The arrests come after over a dozen people were killed and nearly 50 others injured in a suicide bombing in in the St. Petersburg's subway in April.
The two leaders also spoke last week.
"President Trump thanked President Putin for acknowledging America's strong economic performance in his annual press conference," the White House said in a readout of the call.
"The two presidents also discussed working together to resolve the very dangerous situation in North Korea," the White House added.