Nikolic said the beginning of construction provided energy security and employment as well as giving Serbia a chance to clearly show that it had become a country in which it was worth to invest and that it had the workers and the companies for large projects.
He said the pipeline would supply gas to about 35 million households throughout Europe in the long term.
Nikolic said the South Stream pipeline was also a symbol of connecting states and peoples, and that it represented a monument to Serbia-Russia ties.
Serbian Prime Minister Ivica Dacic said two sections of the pipeline would extend to Croatia and the Bosnian Serb entity, and that the Macedonian government was assuring that it would adopt a decision on building a section towards Macedonia as well.
Dacic said he had suggested in talks with Pristina in Brussels that one section go to Kosovo too.
In his note of congratulations, Putin said the construction of the pipeline would be a big contribution to the improvement of international energy security, Itar reported.
He said the project was not only important for Serbia, but for the Balkans and the entire European continent as well.
The South Stream international project is worth about EUR 16 billion and the 421-km-long Serbian section of the gas pipeline is estimated at EUR 1.9 billion. The Serbian section will be built by the South Stream Serbia company, based in Switzerland, in which Srbijagas has a 49 per cent stake and Gazprom 51 per cent.