TOKYO (Yonhap News) – Japan has submitted an official complaint that it is opposed to Seoul's recent claim to an extended portion of continental shelf that reaches beyond South Korea's exclusive economic zone (EEZ) in the East China Sea, local media reported here Saturday.

According to the reports, the foreign ministry in Tokyo presented its opinion to the U.N. Commission on the Limits of the Continental Shelf (CLCS) earlier Saturday. Japan insisted that Seoul and Tokyo need to define their boundaries through consultations and asked the CLCS not to review South Korea's claim.

Last month, South Korea submitted a claim to the CLCS to argue that the Korean Peninsula's natural prolongation of the continental shelf in the East China Sea extends to the Okinawa Trough.

If the CLCS determines that there is a "dispute" over the continental shelf among countries involved, it is to halt its reviewing process. In such a case, the final demarcation will be made through talks among involved parties.

According to the U.N. Convention of the Law of the Sea, coastal nations can claim an economic zone extending 200 nautical miles (370 kilometers) from their shores, and to do so, they are required to document the process of delineating their outer continental shelf and submit the information to the CLCS.

The size of the shelf claimed by Seoul last month is more than double the area of an earlier version, according to the South Korean foreign ministry.

China and Japan have separately claimed the Okinawa Trough, with part of Seoul's recent claim overlapping with China's. Seoul and Beijing, however, share a largely similar stance in defining the limits while being in discord with Japan.

The continental shelf in the East China Sea is believed to be rich in natural gas and oil deposits.   

South Korean officials had said they expected their Japanese counterparts to oppose Seoul's claims, but that they still submitted the information to declare South Korea's right to the trough to the international community.

The CLCS typically puts forth "recommendations" after a three-month, non-regulated review of the information submitted by each country, and its decision is not legally binding.