German Chancellor Angela Merkel joined leaders from the European, French, Dutch and Russian governments in launching the Nord Stream natural gas pipeline.
Russia aims to diversify its European transit options through Nord Stream. The dual pipeline runs from the shores of the Gulf of Finland through the Baltic Sea to Germany.
Construction on the Nord Stream pipeline started in April 2010 and the pipeline was formally launched Tuesday.
"This is a long-awaited event which signifies the strengthening of relations between Russia and the European Union," Russian President Dmitry Medvedev was quoted by state-run news agency RIA Novosti as saying. "This event will enhance the security regime, including energy security in Europe."
Both lines, once fully operational in 2012, will transport around 1.9 trillion cubic feet of Russian gas each year to the European community for at least 50 years.
Conventional routes for Russian natural gas through Soviet-era pipelines in Ukraine are risky because of political spats between Kiev and Moscow. Russian energy company Gazprom cut gas supplies through Ukraine in 2009 because of contact disputes, leaving European consumers in the cold for several weeks.
Nord Stream Managing Director Matthias Warnig said the pipeline gives Gazprom a safe and efficient route to get natural gas to its European consumers.
"This new fixed link between Russia and the EU is one of the long-term solutions for the EU's energy security," he said in a statement.