The Chinese town of Fangchuan at the mouth of the Duman (or Tumen) River that runs through the border with North Korea overlooks both the North's Rajin-Sonbong region and the Russian town of Khasan. The geography has made the North Korean economic zone a hotly contested piece of land between Beijing and Moscow. North Korea shocked China in 2008 by signing a contract with Russia loaning out a port in Rajin-Sonbong for 50 years, recalls Lee Jong-lim at Yanbian University. "That incident prompted China to take a more aggressive approach in developing the Tumen River region."

Vehicles headed for the Rajin-Sonbong economic zone in North Korea wait in line for customs clearance in Hunchun, China on Monday.

In 2009, China produced a blueprint for development of the Changchun, Jilin and Tumen regions along the border with North Korea. "This plan shows that China was not going to wait for multilateral cooperation with South Korea and Russia but take the lead in investing in the region to gain an advantage." South Korea worried that China was trying to turn North Korea into a northeastern province. In 2010, China gained the right to use three ports in the Rajin-Sonbong region and in 2011 it built a freeway linking Hunchun and Rajin port. Beijing also agreed with Pyongyang to build a bridge connecting Hunchun and the North across the Tumen River. Construction of the bridge is reportedly still underway.

Stores in Hunchun, Jilin Province bear signboards in Chinese, Korean and Russian.

Not to be outdone, Russia has decided to include the Tumen River region in a US$23 billion plan to develop its far eastern provinces. And in September last year, Russia repaired an old railway linking Khasan and Rajin-Sonbong. Sung Ki-young at the Korea Institute for National Unification said, "North Korea bolstered economic ties with China after sanctions imposed by Seoul, but then cooperation with China came to a standstill" following the execution of former eminence grise Jang Song-taek, "so Pyongyang stepped up cooperation with Moscow." North Korea is trying to trigger competition between the two big powers. Sung said South Korea too should look into ways of taking part in Tumen River development projects, not only for economic reasons but for political ones as well.