Beijing will "seriously" implement new United Nations sanctions imposed on North Korea over its nuclear and missile programmes, it said Thursday, with the measures set to hit Pyongyang's lucrative Chinese coal exports hard.

UN Security Council resolution 2321, passed on Wednesday, caps the North's annual coal exports at little more than four months of current sales to China, Chinese government data shows.

Spearheaded by the United States, the response to the hermit state's latest nuclear test in September was approved 15-0 after extended negotiations.

It limits North Korea's coal exports next year to 7.5 million tonnes or just over $400 million, down 62 percent on 2015.

The cap represents a fraction of the North's current annual exports to China, the isolated country's sole ally and its main provider of trade and aid.

China imported 1.8 million tonnes of coal worth $101 million from North Korea in October alone, according to the most recent figures available on the Chinese Customs website. The volume was up nearly 40 percent year-on-year.

Beijing will "serious" implement the resolution, foreign ministry spokesman Geng Shuang told reporters at a regular briefing.

China, a veto-wielding permanent Security Council member, had a "responsible attitude", he added, and had always implemented UNSC resolutions and fulfilled "its international obligations according to the UN charter".

Trade with the world's second largest economy is crucial for the isolated and impoverished North, which has suffered regular food shortages and an outright famine in the mid-1990s.

The North's coal exports to the Asian giant have continued unabated despite previous UN sanctions, which included exemptions allowing trade to continue for "livelihood" purposes but did not set criteria for the determination.

"The point here is not the figures", but the legality of the imports, Chinese foreign ministry spokesman Geng Shuang said last week.

The limit in the latest sanctions resolution applies even if the sales are for livelihood purposes.

Although Beijing has traditionally protected Pyongyang diplomatically, believing that Kim Jong-Un's regime is preferable to its collapse, it has grown frustrated by its neighbour's defiance.

Beijing regularly says it "firmly opposes" the North's nuclear tests, but analysts believe it has resisted targeting the country's fragile economy for fear of provoking the regime's collapse.