Officials say a South Korean ship is being held at a domestic port over suspicions that it illegally provided oil to heavily sanctioned North Korea.

A South Korean coast guard official said Wednesday the 5,160-ton P-PIONEER has been prevented from leaving Busan port since October over allegations that it was used to supply oil to North Korea through two ship-to-ship transfers last September in international waters in the East China Sea.

An official from Seoul's Foreign Ministry said it was the first time a South Korean ship was detained over allegations of violating United Nations Security Council Sanctions against North Korea over its nuclear weapons program.

Both officials spoke on condition of anonymity, citing department rules preventing them from speaking to the press.