China's first underground subway line to be built in a frigid region on Thursday started a trial run in Harbin, capital of Heilongjiang Province in the northeast.

The 17.48-km line with 18 stations has been designed to withstand extreme winter cold in the city, which has a record low temperature of 38.1 degrees Celsius below zero.

Trains built by CNR Changchun Railway Vehicles Co. Ltd. for the line can run at 80 km per hour at full speed.

The company said it has used special technology to improve the train's thermal insulation and preservation so that passengers are kept warm despite the outdoor cold.

The subway line linking the city's two railway stations is anticipated to ease traffic pressures on roads in the city, which has a population of more than 10 million.

The city government plans to extend the metro line while building another two lines. The city's total subway line length is expected to reach 89.58 km by 2018.