The revelation comes days after South Korea said it was holding a Hong Kong-flagged ship and crew members over transferring petroleum products to a North Korean vessel in global waters in October.
The crews of both the impounded vessels are mostly Chinese, raising suspicions that China - North Korea's largest trading partner - may be supplying the fuel, or failing to do enough to prevent its sale.
South Korean officials are holding the 5100-tonne, Panama flagged tanker called KOTI in Pyeongtaek-Dangjin after deciding not to let release the vessel on December 21 to investigate further.More news: James Franklin hurting from punch to ribs from Penn State QB
Authorities are now investigating the matter and won't disclose further details, Yonhap reported, adding the ship's crew was mostly made up of citizens from China and Myanmar, just like the Hong Kong-flagged tanker Lighthouse Winmore that was seized on Friday.
They said: "There is no evidence that this is backed by the Russian state - but these Russian vessels are giving a lifeline to the North Koreans". Authorities were not immediately available for confirmation of the report.
The Lighthouse Winmore visited Yeosu on October 11 and loaded some 14,000 tonnes of Japanese refined oil before heading towards its purported destination in Taiwan.More news: Two arrested for grisly family murder
The Russian foreign ministry has denied claims that United Nations sanctions against North Korea had been breached by Russian tankers transferring fuel to North Korean tankers at sea.
Russian Federation denied the reports on Saturday, saying via its foreign ministry that it "fully observes fully the sanctions regime" against North Korea. One was a North Korean vessel, but the Treasury didn't identify where the other ship was from. Only four of the ships on the USA list, the ones belonging to North Korea including Sam Jong 2 and Rye Song Gang 1, were blacklisted at a session held on Thursday, as AFP reported.
The Security Council has imposed three sets of sanctions on North Korea this year: One on Aug 5 targeting the iron, coal and fishing industries, another set on Sep 11 aimed at textiles and limiting oil supply, and the most recent on Dec 22 focused on refined petroleum products.More news: Iranians protest against high prices in Mashhad
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