"Today is remarkable, a truly historic event not only for the global energy market, but first of all for us and for you, for Russian Federation and China", Putin said during a televised ceremony featuring the two leaders.
The pipeline, which Putin has called "the world's biggest construction project", crowns years of tough negotiations and work in hard conditions.
Russian Federation started pumping gas to China on Monday through the Power of Siberia gas pipeline, also known as the eastern route.
Stressing that he and Putin agreed to continue putting bilateral ties as a priority of each other's foreign relations and enhancing strategic coordination and cooperation, Xi called on both countries to redouble their efforts to initiate more key projects like the east-route natural gas pipeline, to boost both countries' development and better benefit both peoples.
"Russia is not only creating new income streams, but hedging its bets and bolstering its position strategically", said energy analyst Andrew Hill.
This is conducive to the realization of a Russia-China trade volume of 200 billion US dollars in 2024, Putin said.
A 30-year purchase and sale contract for the Russian gas supply to China was signed in 2014 by Russian gas corporation Gazprom and the China National Petroleum Corporation (CNPC).
During the video call, China and Russian Federation representatives at northeast China's Heihe station and Russia's Atamanskaya compressor station and Chayandin gas field reported in turn to the two presidents that they were ready to receive or provide natural gas.
Hailing the five-year toil of construction teams from both countries on the project under extreme weather and the completion on schedule, Putin said Russian Federation will provide 1 trillion cubic meters of natural gas to China in the next 30 years.
Gazprom has stressed that the pipeline ran through "swampy, mountainous, seismically active, permafrost and rocky areas with extreme environmental conditions".
Temperatures along the route plunge to below minus 6o degrees Celsius in Yakutia and below minus 40 C in the Russian Far East's Amur Region.
The bridge, which is to open next year, will connect the city of Blagoveshchensk and the northern Chinese city of Heihe.
As its relationships with Europe and the United States have grown more volatile, Russian Federation is looking to bring its vast natural gas resources to the east.
Nord Stream-2, which would double gas volumes to Germany, is expected to go online in mid-2020, though it has faced opposition from the United States and countries in central and eastern Europe, particularly Ukraine.
US President Donald Trump has threatened to hit Nord Stream 2 and those tied to it with sanctions.
The Power of Siberia pipeline is a "project of symbolic importance for China-Russia cooperation", said Xi, who expressed hope that the pipeline will become a driving force for economic and social development in the regions it traverses.