Tianjin Municipality, a major port city in north China, is to have a third subway line at a cost of 12 billion yuan (nearly 1.6 billion U.S. dollars), local authorities announced on Thursday.

The design and construction plan has been approved by the municipal construction committee and development and reform commission, a local government statement said.

The "Number 3" metro line will be 29.7 kilometers long, including 21.7 kilometers that runs underground and a flyover line that stretches 6.9 kilometers, and will have 23 stations.

The line will run from the southwest to the northeast of the city, connecting the two overland rail stations. It is expected to be completed in 2009.

Tianjin started building its first subway line in the 1970s, becoming the second Chinese city to have an underground rail link. The municipality plans to build nine subway lines, with a total length of 234.7 km, within 30 years