The Federal Security Service (FSB) announced last weekend that the men were detained on December 27 based on information from their “American partners.”
Russian President Vladimir Putin on December 29 spoke by telephone with U.S. President Donald Trump to thank him for the intelligence.
In a statement, the local court service identified the suspects as 22-year-old Nikita Semyonov and 23-year-old Georgy Chernyshov.
A St. Petersburg shopping center and a cathedral to where many tourists flock were the alleged targets, the local Fontanka news website reported, citing an FSB source.
The pair had allegedly sent pictures to the Islamic State extremist group confirming the targets.
A video released by the FSB of the raid on the suspects’ residence showed the arrest of the men bearing a Slavic appearance inside an apartment containing munitions, knives, electrical cables, and black clothing, AFP reported.
In October and in 2017, the United States had also shared information about terrorist plots with Russian officials, state TASS news agency reported.