In a bid to further tighten the screws on North Korea's nuclear programme, the United Nations Security Council has imposed additional sanctions on the country's coal exports — its chief source of hard currency.

The new penalties, which were adopted unanimously by the Security Council, will be mainly enforced by China, which is North Korea's principal patron and coal customer. China backed the fresh sanctions adopted on 30 November.

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The New York Times said that backing the new set of restrictions was easy for Beijing as they are aimed at showing its displeasure at Kim Jong-un's nuclear agenda but will not inflict "crippling pain".

It said that the sanctions are unlikely to "upend the North Korean economy and cause social unrest and flows of refugees into China, an outcome it most fears".

Liu Jieyi, China's permanent representative to the UN, said on Wednesday 30 November that North Korea's nuclear tests undermine regional stability and Beijing's "strategic interests". He added that the resolution showed "the uniform stance of the international community".

Samantha Power, the US ambassador to the UN, acknowledged China's cooperation "in working closely with us".

The new sanctions aim to cut $700m from North Korea's coal revenues, imposing a 7.5 million metric tonne limit of coal that can be exported a year, or not more than $400 million in sales.

It requires countries to inform the UN how much coal they are buying from North Korea. It also expands the list of banned imported items, which now covers luxury goods like bone china and equipment with dual-use purposes. The UN resolution also bans copper, nickel, silver and zinc exports, and the sale of statues by Pyongyang.

North Korean diplomatic missions around the world are also now to be allowed only one bank account, in a move to limit the use of envoys and embassies to further its nuclear programme. The newspaper said the measures were in response to Kim's fifth and largest nuclear test.

Reuters said that the council also blacklisted 11 individuals, including former ambassadors to Egypt and Myanmar, and 10 entities. They are subject to global travel bans and an asset freeze for their roles in North Korea's nuclear and ballistic missile programme.

The news agency said that China is believed to be the only country that buys North Korean coal. In the first 10 months of 2016, China imported 18.6 million tonnes of coal from North Korea, up almost 13% from a year earlier.

Diplomats told the agency that banning the exports of copper, nickel, silver and zinc will cut $100m in revenue while the ban of statue sales, mainly to African countries, will remove tens of millions of dollars in revenue.

North Korea