East Asia is the region containing a range of territorial disputes, which occasionally escalate into regional violence such as Takeshima/Dokdo islands of Japan and South Korea and Yeonpyeong Island dispute of North and South Korea. Maybe many of the island territories are small, isolated and sparsely populated but only strategic interests and abundant natural resources make them more and more valuable. Have a look at this interesting article about top island disputes in East Asia.
Takeshima/Dokdo islands – claimed by Japan and South Korea
Dokdo Island by Korea or Takeshima by Japan is 215 kilometers from mainland Korea and 250 kilometers from Japan proper. This island chain was claimed by Japan in 1905 prior to its annexation of the Korean peninsula but South Korea denied this claim and said that the islands became its territory when it declared independence in 1945. On 4th August, Donga Ilbo newspaper of South Korea reported that the South Korean government was planning to build more infrastructure on Dokdo. On the same day, Yoshitaka Shindo Lawmakers said he would continue to visit the disputed Takeshima/Dokdo, making the islands be in spotlight this week. Tensions also flared in January 2011 after Japan arrested the captain of a South Korean fishing vessel that had floated into the disputed territory.

Both Japan and Korea laid claim to Dokdo and both claimed a long historical and geographical connection with the islets
Diaoyu/Senkaku islands – claimed by China and Japan
Diaoyu/Senkaku islands containing sizable petroleum reserves were previously controlled by Taiwan as part of China but following the Sino-Japanese War, Japan took over them. Despite Chinese disagreement, the US and Japan signed a treaty returning Okinawa and the islands to Japanese control in 1971.

Diaoyu/Senkaku islands
Southern Kuril Islands – claimed by Japan and Russia

According to Soviet claims, the islands of Etorofu and Kunashiri and the Shikotan and Habomai islets are a part of the Kuril Islands in 1945 Japan maintains that they are an integral part of the Japanese home islands, illegally seized by the Soviet Union
Spratly Islands – claimed by China, Malaysia, Philippines, Taiwan, Vietnam, and Brunei
The Spratly Islands spreading over 150,000 square miles in the South China Sea includes 190 islets in an archipelago. There are many countries laid their claim in the islands that hold potentially significant oil and gas reserves. While China claims the entire South China Sea, while the other countries such as Malaysia, Philippines, Taiwan, Vietnam, and Brunei claim parts of it.

In July 2011, China and the Association of Southeast Asian Nations managed to make a tentative agreement on “behavioral guidelines” in this region in spite of the fact that it did not solve the conflicting territorial claims
Yeonpyeong Island – claimed by North Korea and South Korea

On the maritime border of North and South Korea, Yellow Sea there are Yeonpyeong Island listed on East Asia's top island disputes when occasionally escalated tensions in 2010
Top Island Disputes in East Asia in Pictures: Yeonpyeong Island
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Top Island Disputes in East Asia in Pictures