BEIJING -- Construction began Thursday on the Guiyang-Nanning high-speed railway, part of broader efforts to develop the China's less prosperous southwest region.

With a length of 482 km, the railway line will cut travel time from Nanning to Guiyang from over 10 hours to 2 and a half hours, said Ding Rongfu, chairman of China Railway Airport Construction Group Co.

With a maximum speed of 350 km per hour, the line is expected to go into service in 2022.

Construction will be difficult due to complicated geography and landform, Ding said, adding that 106 tunnels have to be excavated along the line.

China has more than 20,000 km of high-speed railways. According to a government plan, mileage will increase to 45,000 km by 2030.