Police arrested two terrorism suspects in Russia after a US tip about a possible terrorist attack in St. Petersburg. On Monday, a court ordered the detention of the two men, identified as Nikita Semyonov and Georgy Chernyshev, who had sworn their allegiance to the IS in a video. Both suspects will remain in detention pending their trial. The Federal Security Service (FSB), the main KGB successor agency, said in a statement that the suspects detained on Friday confessed to plotting the attacks. It added that it also seized materials proving their guilt. The FSB said it was acting on a tip provided by its “American partners.” On Sunday, Russian President Vladimir Putin called U.S. President Donald Trump to thank him “for information transmitted through the special services that helped prevent terrorist attacks in Russia,” according to the Kremlin. Videos released by the FSB showed its agents rounding up the two suspects and searching their homes. Putin’s spokesman Dmitry Peskov said Monday that the information provided by the U.S. was a “vivid proof of the efficiency” of counter-terrorism cooperation between the two countries. In December 2017, Putin similarly thanked Trump for a CIA tip that helped thwart a series of bombings in St. Petersburg. The Kremlin said then that the CIA information led the FSB to nab a group of suspects that planned to bomb St. Petersburg’s Kazan Cathedral and other crowded sites.