South Korea has revealed it seized a Hong Kong-registered ship last month suspected of supplying oil to the North in breach of international sanctions.
Officials said the Lighthouse Winmore had secretly transferred 600 tons of refined oil to a North Korean ship.
A UN Security Council resolution bans ship-to ship transfers of any goods destined for Pyongyang.
The revelations came as China denied claims by President Donald Trump it had allowed oil shipments to the North.
On Thursday the US president tweeted he was “very disappointed” with China, which he said had been “caught red-handed”. He was responding to a South Korean report that suggested Chinese ships had been spotted selling oil to North Korean ships at sea in recent weeks.
Although the Lighthouse Winmore is Hong Kong-flagged, it leased by a Taiwanese company.
The Chinese government swiftly rejected the president’s claim, saying it was “not consistent with the facts”.
“China has never allowed Chinese enterprises nor individuals to violate UN Security Council resolutions imposed on the DPRK,” foreign ministry spokesperson Hua Chunying said.
The Lighthouse Winmore entered Yeosu port in South Korea on 11 October to load up with refined oil and left bound for Taiwan, Yonhap news agency reported.
But instead of going to Taiwan it transferred the oil to a North Korean ship and three other vessels in international waters, South Korean officials were quoted as saying.
The Lighthouse Winmore remains in South Korea, the authorities told the BBC Korean service.
President’s Trump latest broadside against China came after South Korean newspaper Chosun Ilbo reported that Chinese tankers had been secretly transferring oil at sea to North Korean vessels.
Quoting South Korean government officials, it said the illegal ship-to-ship transfers had been filmed by US spy satellites about 30 times since October.
China, North Korea’s main trading partner, has repeatedly said it fully enforces all UN resolutions against Pyongyang. -BBC