South Korea has seized a Hong Kong-flagged vessel suspected of transferring oil to North Korea in defiance of international sanctions, a foreign ministry official said.
The vessel, Lighthouse Winmore, transferred refined petroleum products to a North Korean ship in international waters in late October, the official told Reuters.
The United States proposed blacklisting the Hong Kong-flagged ship to the UN Security Council for circumventing sanctions slapped on North Korea for its nuclear and missile programs, documents seen by Reuters this month showed.
China said on Friday that reports of Chinese ships selling oil to North Korea did not accord with the facts, adding that China would never allow Chinese companies to violate UN resolutions.
China had always implemented UN resolutions in their entirety, ministry spokeswoman Hua Chunying told a daily news briefing.
She said if there really were violations, China would deal with them seriously in accordance with the law.
Hua was speaking after US President Donald Trump said he had "been soft" on China on trade issues and said he was not happy that China had allowed oil shipments to go into North Korea.