North Korea's trade with China has nearly tripled since 2007, data published by South Korea showed Thursday, underlining the isolated state's deepening dependence on its only major ally.

Bilateral trade jumped from $1.97 billion in 2007 to $5.6 billion last year, Statistics Korea said, with North Korean exports accounting for $2.44 billion against imports from China of $3.16 billion.

Statistics Korea releases the annual data based on figures from trade and economic organisations at home and abroad. The North does not report economic data.

Trade with China as of last year accounted for 70.1 percent of the North's entire trade of $8.0 billion, up from 41.7 percent in 2007.

During the same period, trade with South Korea -- the North's second-biggest partner -- fell from $1.79 billion to $1.71 billion.

Cross-border relations have been on ice since outgoing President Lee Myung-Bak, known for his hawkish stance towards the communist North, took office in 2008.

Lee suspended humanitarian aid to the North in 2010 and tied any resumption to progress on resolving the issue of Pyongyang's nuclear programme.

Inter-Korea commerce, which accounted for 38 percent of the North's total trade in 2007, was down to 21 percent last year.

Apparently fearful of the consequences of North Korea collapsing, China has pumped in fuel and aid to its neighbour for years.

The nuclear-armed North is subject to international sanctions imposed after its nuclear tests in 2006 and 2009, and those may be tightened or expanded following it's successful long-range rocket launch earlier this month.

Pyongyang said the launch was a purely scientific mission, but most of the world condemned it as a disguised ballistic missile test that violated existing UN resolutions.