Russian President Vladimir Putin said on Thursday that he was grateful to Saudi Arabia's Crown Prince Mohammed bin Salman for helping to organize the biggest U.S.-Russian prisoner swap since the Cold War. U.S. journalist Evan Gershkovich and ex-U.S. Marine Paul Whelan returned to the United States on Aug. 1, hours after being freed from Russian detention in the biggest prisoner exchange between the two countries since the Cold War. The swap deal, worked on in secrecy for more than a year, involved 24 prisoners - 16 moving from Russia to the West and eight sent back to Russia from the West. "Saudi Arabia's Crown Prince played an active role in the initial stages of this work. We are very grateful to him, as it resulted in the return of our citizens to the homeland," Putin said at the Eastern Economic Forum. Putin also thanked Turkish President Tayyip Erdogan for providing the venue for the exchange. He mentioned that several other Arab countries facilitated the swap but did not name them.