Gazprom Board deputy chair Alexander Medvedev signed the contract on Wednesday with the president and director-general of the Hungarian gas company MVM, Csaba Baji.
The signatories approved the final investment plan for the construction of the 229-kilometre-long Hungarian section of the pipeline.
Croatian media reported a few months ago that Russia's decision on South Stream was expected and that Croatia and Hungary shared equal chances of getting the transit route. The Croatian section would be significantly shorter, which would reduce the construction price, it was reported.