China and Russia signed on Monday an agreement on the return of 174 square kilometers of territory on their northeastern border to China, thereby also completing the demarcation of the Sino-Russian border.

The protocol was signed by Chinese Foreign Minister Yang Jiechi and visiting Russian Minister of Foreign Affairs Sergei Lavrov in Beijing.

The agreement ends over 40 years of negotiations over the governance of Yinlong Island (Tarabarov Island) and half of Heixiazi Island (Bolshoi Ussuriysky Island). The areas lie in northeast China, at the junction of the Heilongjiang river and the Wusulijiang river.

The handover deal was settled in October 2004, when Vladimir Putin, then Russian president, visited China. Subsequent delineation work around the islands took three years, according to The China Post.

Russia took control of Heixiazi and the Yinlong Islands in 1929, The China Post writes. In Chinese, the area is collectively referred to as the Heixiazi Islands. In the 1960s and 70s, the struggle over the control of the contested land resulted in a number of violent clashes between the two neighbors.

On July 17, Russian Minister-Counselor in China, Igor Morgulov, announced that all disagreements concerning the territory's handover had been solved and Russia was ready to complete the deal. The formal transfer of control will take place in August, thus completing the process of demarcating the 4,300-kilometer Sino-Russian border.

Lavrov, in Beijing until Tuesday, is also scheduled to meet President Hu Jintao and Premier Wen Jiabao during his visit.

Sino-Russian relations have warmed considerably in recent years, due to a mutual desire to counter US influence in world affairs. China is also keen to secure access to Russia's natural energy resources, according to AP.