China has apparently obtained considerable rights to build and use facilities in a special North Korean district.

A source in Beijing says the two sides signed a deal on the construction of infrastructure in the special district late last year around the time of North Korean leader Kim Jong-il's death.

The source says the deal allows China to build three piers in the Rason district and use them for the next 50 years. China was apparently also given permission to build an airfield and a thermoelectric power plant in the district and lay a 55 kilometer railway connecting Tumen in China's Jilin province to Rason.

China will first begin building the No. 4 Rajin Port pier, which will be able to accommodate 70-thousand tons of vessels. It's also known to be investing three billion dollars by 2020 also for the airfield and rail constructions.

News of the deal has raised concerns of fairness and worries that the North Korean district may be incorporated into the Chinese economy.