Illicit trade at sea poses a governance challenge around the globe, Chinese experts say, after ships were found transferring oil to North Korean vessels in the Yellow Sea in breach of tough new UN sanctions. Details of the fuel transfers – including the location and whether governments played a role – still needed to be investigated, they said. The assessment came after US satellite images showed a Hong Kong-registered ship transferring oil to a North Korean vessel in international waters in October, and media reports said Russian tankers had also supplied fuel to the North at sea in recent months. Twenty-five crew members of the Lighthouse Winmore – registered in Hong Kong and chartered by a Taiwanese company – have been detained for questioning in South Korea since the tanker was impounded in November at Yeosu, according to customs officials at the port. Crew of Hong Kong ship accused of transferring oil to North Korean vessel questioned in South Korea Ship-to-ship transfers at sea of any goods destined for North Korea violate a United Nations Security Council resolution imposed on Pyongyang in September as it again tried to rein in the pariah regime. On Thursday, US President Donald Trump accused China of violating sanctions meant to halt North Korea’s nuclear weapons programme. “Caught RED HANDED – very disappointed that China is allowing oil to go into North Korea,” Trump said via Twitter on his personal handle. Speaking later to The New York Times , Trump said: “If they don’t help us with North Korea, then I do what I’ve always said I want to do.” But experts in China said that by making accusations before the details had been confirmed, Trump was not helping already strained Sino-US relations. “Smuggling is very hard to eradicate – it’s a challenge for every government. We can see that even the US government can’t stop the flow of illicit drugs from Mexico over a land border,” said Sun Xingjie, a specialist in North Korean affairs at Jilin University. “Trump’s tweets reflect a simplistic attitude to the North Korea issue, totally ignoring that it’s becoming increasingly more difficult to stifle Pyongyang’s [nuclear ambitions] through sanctions,” said Sun, adding that the US president’s remarks only added to the problem. Will 2018 see war in North Korea? Chances soar after year of tumult The UN Security Council has imposed three rounds of sanctions on North Korea this year: on August 5, targeting the iron, coal and fishing industries; on September 11, aimed at textiles and limiting oil supply; and on December 22, mainly on refined petroleum products. The most recent sanctions were a response to North Korea’s test launch of an intercontinental ballistic missile in late November that it said was capable of reaching mainland US cities. Pyongyang slammed the latest sanctions as an “act of war” and on Saturday, the state-run KCNA news agency said in a commentary that the country would continue to pursue its nuclear ambitions. Zhang Liangui, an international relations professor at the Central Party School in Beijing, said it was difficult for the Chinese authorities to monitor activities on the high seas. North Korea relies on imported fuel to keep its struggling economy functioning. It also requires oil for its missile and nuclear programme that the United States says threatens the peace in Asia.