Two Russians were detained on December 27 on suspicion of plotting attacks during New Year festivities in Saint Petersburg.
Russia said on Sunday it had thwarted terrorist attacks reportedly planned in Saint Petersburg thanks to a tip from Washington, bringing personal thanks again from President Vladimir Putin to his US counterpart Donald Trump.
Russian news agencies cited the Federal Security Service (FSB) as saying that thanks to the information, two Russians were detained on December 27 on suspicion of plotting attacks during New Year festivities in Saint Petersburg.
The Kremlin said Putin passed on his gratitude to Trump during a phone call on Sunday for the tip from US special services. It gave no more details.
Diplomatic ties between Washington and Moscow are fraught over disagreements from Ukraine to Syria and allegations of Russian meddling in the US presidential election, but Trump and Putin have managed to keep personal lines open.
Two years ago, the Russian leader also phoned Trump to thank him for a tip that Russia said helped prevent a bomb attack on a cathedral in Saint Petersburg. Russia has repeatedly been the target of attacks by militant groups including Daesh.
Sunday's Kremlin statement said Putin and Trump agreed to continue bilateral cooperation to tackle terrorism.