Vladimir Putin visited Seoul in February 2001, while South Korean president Roh Muhyeon visited Moscow in September 2004. South Korea and Russia are participants in the Six-party talks on the North Korea's nuclear proliferation issue. In November 2013, Russia and South Korea signed a visa-free travel regime agreement. From 21 to 23 June 2018, South Korean president Moon Jae-in paid a state visit to Russia. On June 21, he addressed the State Duma, the lower house of the Russian Federal Assembly. He became the first South Korean leader to speak in the Russian Parliament. On June 22, Russian President Vladimir Putin held talks with Moon Jae-in in Moscow. Leaders signed a document for foundation of free trade area. On 28 August 2018 Vice Defense Minister Suh Choo-suk met with Russian counterpart Alexander Fomin and reached an agreement to install a direct communication line between their air forces of two countries. In March 2022, Russia placed South Korea on the Unfriendly Countries List during the 2022 Russian invasion of Ukraine. Economic cooperation South Korea and Russia are working together on construction of a bilateral industrial complex in the Nakhodka Free Economic Area in Russia's Far East and gas-fields development in Irkutsk. The two sides also agreed to cooperate on reconnecting a planned inter-Korean railroad with the Trans-Siberian Railway. Russia has expressed interest in becoming a conduit for South Korean exports to Europe, which now go by ship, by linking the Korean railroad to the TSR. Russia reportedly offered to repay its $1.7 billion debt to South Korea through joint investments in North Korea, such as the railroad project. Space program South Korea sent its first cosmonaut on board a Soyuz flight to the International Space Station in April 2008. South Korea made domestic satellite launches in 2009 and 2010, both with Russian assistance. The first South Korean satellite was successfully launched in 2013 with extensive Russian assistance and a Russian first stage. North Korean nuclear threat After the nuclear test on May 25, 2009 for which North Korea was facing much censure from many countries, Pyongyang has threatened to attack South Korea after it joined a U.S.-led plan to check vessels suspected of carrying equipment for weapons of mass destruction. Many news agencies in Moscow were fearing that this move may lead to nuclear war. North Korea also threatened many other countries such as the US and other federations across the