MOSCOW, May 26 (AFP) - President Boris Yeltsin interrupted his Black Sea vacation Wednesday and flew back to Moscow on the eve of an official visit to Russia by South Korean leader Kim Dae-Jung, television reports said. Yeltsin, 68, departed his Sochi resort at 3:00 p.m. (1100 GMT), a correspondent travelling with the president reported. The Kremlin chief, who left for what was planned as a two-week holiday six days ago following reports of poor health which the Kremlin later denied, is due to meet Kim in the Russian capital on Friday. Kim's three-day visit to Moscow is his first as president, although the South Korean leader studied political science in Moscow in 1992. During his stay Kim is expected to discuss a range of trade issues with his Russian counterpart, and move to mend ties hurt during a damaging tit-for-tat spy expulsions row last summer and a delayed loan repayment. The spy row erupted last July when Moscow expelled a South Korean diplomat allegedly caught red-handed as he bought information from a Russian foreign ministry official. It escalated when Seoul expelled a Russian diplomat in retaliation, straining nine-year-old ties between the former Cold War enemies. The two leaders are also expected to discuss international and regional problems, including stability on the Korean peninsula, Kremlin officials said. Russian trade officials told the Interfax news agency that the two sides would sign a deal to build an industrial complex in the far eastern port of Nakhodka, in which South Korean firms could invest up to 800 million dollars. The site would be developed by the Korean Land Corporation which plans to develop 330 hectares (825 acres) of land in the area, rented for a period of 50 years. Other documents to be inked during the visit concern civilian nuclear energy; economic cooperation in the Russian republic of Buryatiya, eastern Siberia; and a memorandum on industrial cooperation. South Korea is also interested in an 8-10 billion dollar project to export Russian gas from the Kovyktinskoye condensate field to China and then on to the Korean peninsula. Two-way trade is currently languishing, with commercial exchanges worth just two billion dollars in 1998. Russian exports included aluminium, scrap iron, steel, nickel, synthetics, fish products and meat, while South Korea shipped machinery, oil exploration equipment, televisions, vehicles, and refined oil products to Russia. Direct investment by South Korea in Russia is also low at just 194 million dollars as of January 1, 1999.  