Sanctions against North Korea over its nuclear programme are not "the fundamental way" to resolve the crisis, China's foreign minister said Saturday, days after the UN tightened measures against Pyongyang.

China is the North's sole major ally and by far its biggest trading partner, including being its primary energy supplier. 

It voted Thursday for the UN resolution that stiffened restrictions on North Korea's financial dealings, notably its suspect "bulk cash" transfers, and blocked imports of some luxury goods, following Pyongyang's nuclear test last month.

"The DPRK conducted a third nuclear test and tensions on the Korean peninsula once again heightened," Foreign Minister Yang Jiechi told reporters in Beijing, using the North's official name. "This is not something we want to see."

But he added: "We always believe that sanctions are not the end of Security Council actions, nor are sanctions the fundamental way to resolve the relevant issues."

Reiterating China's longstanding position, he called for dialogue and negotiations, including a resumption of the six-party talks process, which has been moribund since 2009.

"We call on all relevant parties to bear in mind the larger interest, stay calm, exercise restraint and refrain from taking any move that may further worsen the situation," he added. 

Since the UN resolution was passed the North has responded with fresh threats of nuclear war, vowing to scrap peace pacts with South Korea as its rhetoric reached a frenzied pitch. 

In Chinese strategic thinking, North Korea is a "buffer zone" that prevents the 28,500 US troops stationed in South Korea encroaching on its own border.

But analysts say that Pyongyang's actions mean the relationship risks becoming an irritant for Beijing. (AFP)