Passengers walk out of a subway train linking Shanghai and Kunshan in Jiangsu province, Oct 16. [Photo/CFP]

China's first trans-provincial subway line, linking the country's commercial hub of Shanghai with Kunshan city in neighboring Jiangsu province, opened on Wednesday.

The six-kilometer extension of Shanghai Metro Line 11 was built with a cost of 1.85 billion yuan ($301 million).

The extension linking the two cities features three elevated stations: Zhaofeng Road Station, Guangming Road Station and Huaqiao Station in Kunshan. With the extension, the length of Metro Line 11 grew to 72 km, making it the longest subway line in Shanghai.

The trip from Huaqiao Station in Kunshan to downtown Shanghai now takes about an hour and costs 7 yuan.

"It saves me more than 20 yuan every day," said Ma Xiaoya, a resident of Kunshan who works in Shanghai.

Before the extension, Ma had to take a train from Kunshan to Shanghai and then take the subway to arrive at her workplace.

The cities of Suzhou and Wuxi, both in Jiangsu province, are also planning to construct light rail lines linking the cities to Shanghai's subway system.