Seoul: North Korean leader Kim Jong-Un wished his Chinese counterpart Xi Jinping "great success" in a congratulatory but comparatively restrained message after he cemented his grip on power at a landmark Communist Party Congress.  

Kim's note extended "sincere congratulations" to the Chinese president, who was formally given a second term as the head of the ruling party, state-run KCNA said today. The message, sent Wednesday, also "expressed conviction that the relations between the two parties and the two countries would develop in the interests of the peoples of the two countries," KCNA said.  

But the brief, four-sentence missive was a notable contrast to the fulsome terms in which Kim praised the Chinese leader and his country when Xi ascended to power five years ago. Ties between the two neighbours have soured in recent years as the North staged a series of nuclear tests and missile launches despite opposition by Beijing -- its sole diplomatic ally and economic lifeline.  

In 2012 Kim described the two nations as "friendly neighbours linked by the same mountain and rivers" and bilateral ties as the "common precious wealth associated with the wisdom and efforts of the leaders of the elder generations".  

Beijing has been reluctant to slap sanctions harsh enough to rattle the North's political status quo over fears that its collapse could send an influx of refugees across their shared border and place the US army at China's doorstep.  

But in a sign of irritation at its unpredictable neighbour, Beijing cut all its coal imports from the North earlier this year and voted in favour of broader UN sanctions imposed on Pyongyang in recent months.