According to Yonhap:
North Korea owes a total of $18 billion to 30 different countries, including Russia and China, said Kwon Young-se of the ruling Grand National Party (GNP), citing estimates from the Unification Ministry.
The amount is almost equal to North Korea’s gross domestic product (GDP) for last year, which totaled 24.7 trillion won ($18.4 billion).
South Korea has loaned roughly 1.19 trillion won to the North, equivalent to nearly five percent of Pyongyang ‘s total foreign debt.
…
“North Korea’s foreign debt is the result of the accumulation of unpaid trade bills and loans that it received from socialist states in the 1950s and 60s and from the Western world in the 70s to develop its economy,” Kwon said.
“The volume of foreign debt is expected to continue to rise due to the interest added to unpaid debts, although that can fluctuate depending on the result of negotiations with foreign creditors,” he added. (Yonhap)
According to the CIA world factbook, however, North Korea’s total external debt was estimated at $12.5 billion in 2001. If I put aside the fact that the South Korean Ministry of Unification and the US CIA are probably reporting dollar figures using different basis years, North Korea’s external debt has increased increased nearly 47% in the last seven years. I do not think this drastic increase could be attributed to the accumulation of interest arrears dating back to the 1950s.