South Korea has rejected Japan's protest against Seoul conducting a marine survey in waters off the Dokdo islets in the East Sea. 

Japan’s foreign ministry said it found a South Korean research vessel was carrying out a marine survey on Thursday, intruding into what it claims to be the Exclusive Economic Zone around Takeshima, the Japanese name for the Dokdo islets.

The ministry added that Seoul did not seek prior approval for the survey from Tokyo. 

An official from the South Korean foreign ministry dismissed the protest, saying that Dokdo is South Korea's own territory historically, geographically and by international law and that no sovereignty claims to Dokdo by Japan can be accepted. 

The official added that the government cannot accept Japan’s protest against the research activity which was legitimately carried out in accordance with related laws.