South Korea has pushed back against Tokyo's protest over a maritime survey Seoul conducted in Japan's exclusive economic zone near the Takeshima Islands.

South Korea controls the islands in the Sea of Japan. Japan claims them.

The South Korean Foreign Ministry said on Monday that it cannot accept a complaint from Japan because the survey is a legitimate activity conducted based on international and domestic laws.

Tokyo filed the protest after the Coast Guard found a South Korean research ship in Japan's EEZ near the islands on Sunday. Japan's Foreign Ministry said the vessel was spotted dropping what looked like a wire into the waters.

Funakoshi Takehiro, who heads the ministry's Asian and Oceanian Affairs Bureau, protested against the ship's activity and called for an immediate cessation.

He said the maritime survey in Japan's EEZ violates a UN convention as it was carried out without Tokyo's prior consent.

The Japanese government maintains the Takeshima Islands are an inherent part of Japan's territory. It says South Korea is illegally occupying them.