Tokyo has stepped up its rhetoric over claims that Okinotorishima is an island and not rocks under international law in the wake of a tribunal ruling in The Hague this week on the South China Sea.

On Tuesday, the Permanent Court of Arbitration found in favor of the Philippines in its territorial dispute with China, saying that Beijing had no "legal basis" to claim "historic rights" to islets in the waters.

Adding to the geopolitical fallout, analysts say the decision could potentially undermine Japan's claim to Okinotorishima, which it administers, but which is also claimed by Taiwan and is geographically similar to the South China Sea islets.