It will have a full-year capacity of 25,000 units, employing over 700 people producing the Chevrolet Captiva SUVs for the Russian market and a new generation of compact cars from kits.
GM is also starting production at a separate site in St Petersburg which will produce semi-knocked down versions of the Captiva, which will open in September.
Total investment in the new facilities amounts to $115 million (£78.3m).
Nissan has also finalised its plans for a new manufacturing plant in St. Petersburg by signing an agreement with the ministry of economic development and trade of the Russian federation.
Nissan first unveiled its plan to invest $200 million (£137m) in a new assembly plant in St. Petersburg in April this year.
Production will begin in 2009 and when fully operational, the plant will employ 750 people with a currently planned capacity of up to 50,000 units per year. The plant will produce at least three different models specifically adapted for the Russian market.