Abagaitu Islet is an islet in the Argun River (Asia)

Argun River (Asia)

Ergune or Argun is the river which is a part of the Russia–China border. Its upper reaches are known as Hailar River in China. Its length is 1,007 mi...

 divided between the People's Republic of China

People's Republic of China

China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

 (Inner Mongolia Autonomous Region) and Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 (Chita Oblast

Chita Oblast

Chita Oblast was a federal subject of Russia in southeast Siberia, Russia. Its administrative center was the city of Chita. It had extensive international borders with China and Mongolia and internal borders with Irkutsk and Amur Oblasts, as well as with the Buryat and the Sakha Republics. Its...

). Area 58 km².

The island was occupied by the Soviet Union in 1929, a move not accepted by China, resulting in a border dispute that lasted more than seventy years.

On October 14, 2004, the Complementary Agreement between the People's Republic of China and the Russian Federation on the Eastern Section of the China–Russia Boundary was signed, in which Russia agreed to relinquish control over a part of Abagaitu Islet. In 2005, the Russian Duma and the Chinese National People's Congress approved the agreement.