Subway Line 4 goes into operation in Shenzhen, Guangdong province, June 16, 2011. [Photo/Xinhua]

SHENZHEN - The southern Chinese city of Shenzhen's Line 4 subway went into operation Thursday afternoon, seamlessly connecting Shenzhen and Hong Kong for the first time.

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The 20.5-km subway line starts at Qinghu Station in north Shenzhen to Futian Port Station in the south. The Futian Port station connects to Hong Kong's East Rail Line.

Passengers can also use the subway line's Shenzhen North Station to connect to the Guangzhou-Shenzhen-Hong Kong high-speed railway and the Xiamen-Shenzhen dedicated passenger line.

Xu Qin, mayor of Shenzhen, said on Thursday at the line's opening ceremony that the opening of the line will have great significance for regional economic development.

Henry Tang Ying-yen, chief secretary for administration of the Hong Kong SAR, said the new line is conducive to further cooperation in economy and people's livelihoods between Shenzhen and Hong Kong.

The subway line was built and is operated by the Hong Kong MTR Corp., Ltd. The line was built at a cost of 6 billion yuan over the course of 6 years.