Work on a 3.6-km-long tunnel under the Yangtze River, which will carry a section of subway Line 10 in Nanjing, capital of Jiangsu province, was completed on Friday.

It is the longest tunnel under a river in China, according to Xinhua News Agency.

Workers spent three years on the project, with investment of 820 million yuan ($133 million), the report said.

Wang Shouqiang, the project manager, said the geological conditions in the tunnel are very complicated and workers had to overcome many obstacles in its construction.