A new report says North Korea's trade with China accounted for more than 70 percent of its total commerce last year, as the isolated nation deepens its reliance on its only major ally.

South Korea's national statistics office said Thursday that Pyongyang's bilateral trade with Beijing totaled over $5.6 billion in 2011. That is an increase of over 60 percent from the previous year.

Seoul says it is the first time that North Korea's trade with China has topped 70 percent of its global commerce since it began tracking trade figures in 2000.

Facing increasing international isolation, North Korea has relied heavily on China, which provides the impoverished country with economic aid and diplomatic defense at the United Nations.

The U.N. Security Council is considering tightening sanctions against Pyongyang following a successful long-range rocket launch this month. The Security Council condemned the launch as a disguised missile test banned under existing sanctions.

Worsening cross-border relations also affected inter-Korean commerce. The report said the North's trade with South Korea, its second biggest trading partner, fell to 21 percent of its global total in 2011.

Meanwhile, the economic gap between South Korea and North Korea continues to be large. The report found South Korea's gross national income per capita ($1239) was nearly 19 times that of the North in 2011.

The annual report is based on data from international research institutes, since North Korea does not release economic figures.