Construction of a 12.3-kilometer railway tunnel linking Dali and Lincang in Yunnan province completed on Tuesday, according to the railway's project department with China Railway 12th Bureau Group Co Ltd.

It marks the country's first tunnel longer than 10,000 meters in the longitudinal valley zone of the Hengduan Mountain range in southwestern China, the department said.

Named Xinhua Tunnel, it sits in Nanjian county of Dali Bai autonomous prefecture and passes through a connecting part of Wuliang Mountain and Ailao Mountain featuring complicated geological formations.