Turkey has given the go-ahead for the construction of a gas pipeline under the Black Sea, Russia's energy giant Gazprom said.
Russian prime minister Vladimir Putin has received the written permission for South Stream from visiting Turkish energy minister Taner Yildiz.
The South Stream project is meant to transport Russian natural gas to Europe under the Black Sea. The pipeline, which is expected to start in 2015, would ship the gas to southern and eastern Europe.
The permission was the final hurdle to the pipeline's construction, and Gazprom's chief executive, Alexei Miller, described it as "the most serious proof" that the project will be completed by 2015.
South Stream is rivalling an EU-backed Nabucco pipeline which is set to ship gas from the Caspian region to Austria.