Nord Stream AG, the operator of a gas pipeline intended to bring Russian natural gas to Germany under the Baltic Sea, has completed underwater work on the first pipeline, the operator said on Tuesday.

"All three sections of the first of Nord Stream's twin 1,224 kilometer natural gas pipelines have now been joined together underwater by hyperbaric tie-ins. The completed pipeline through the Baltic Sea will now be prepared for connection to the landfalls in Russia and Germany later in the summer," the operator said in a statement.

The pipes of the first line were welded together on board special pipelay vessels and laid on the seabed along a precisely defined route which had been agreed with the authorities of the five countries through whose waters the pipeline passes: Russia, Finland, Sweden, Denmark and Germany. The two main pipelay vessels used for the first line are currently laying the second pipeline in the Gulf of Finland, the operator said.

"Work on the second pipeline is progressing at the rate of about six kilometers a day, and more than 230 kilometers have already been constructed. When both lines are fully operational by the end of 2012, the Nord Stream pipeline will be capable of transporting 55 billion cubic meters (bcm) of gas a year to Europe," the operator said.

Russia's gas giant Gazprom, which holds 51 percent in Nord Stream, has already signed long-term contracts on gas deliveries via the Nord Stream pipeline with several European countries, including Germany, Denmark, the Netherlands, Belgium, France and the UK.