A fleet of North Korean cargo ships is heading home to the port of Nampo, the majority of it fully laden, after China ordered its trading companies to return coal from the isolated country, shipping data shows.
Following repeated missile tests that drew international criticism, China banned all imports of North Korean coal on Feb. 26, cutting off the country's most important export product.
To curb coal traffic between the two countries, China's customs department issued an official order on April 7 telling trading companies to return their North Korean coal cargoes, said three trading sources with direct knowledge of the order.
Shipping data on Thomson Reuters Eikon, a financial information and analytics platform, shows a dozen cargo ships on their way to North Korea's main west coast port of Nampo, almost all carrying cargoes from China.
Chinese authorities did not respond to requests for official comment.
U.S. President Donald Trump and Chinese President Xi Jinping were discussing North Korea at Trump's Mar-a-Lago resort on April 7.
The Trump administration has been pressuring China to do more to rein in North Korea, which sends the vast majority of its exports to its giant neighbor across the Yellow Sea.
But U.S. Secretary of State Rex Tillerson has said last week's U.S. military strike against Syria over its alleged use of chemical weapons was a warning to other countries, including North Korea, that "a response is likely" if they pose a danger.
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As a U.S. Navy strike group headed to the region in a show of force, China and South Korea agreed on Monday to slap tougher sanctions on North Korea if it carries out nuclear or long-range missile tests, a senior official in Seoul said.
North Korea marks several major anniversaries this month and often marks the occasions with major tests of military hardware.