China will invest over $ 390 million to build its first undersea tunnel in Xiamen in China's Fujian Province.

The State Development and Reform Commission approved a feasibility report of the East Passage Project in February, the government said on Friday.

The tunnel will connect the island of Xiamen and the neighbouring mainland. It will be about nine-km long and 70 metres underwater, the government said.

The tunnel, which will be completed by 2010, will have six lanes and a top speed of 80 km per hour.

Xinhua news agency reported the construction is expected to commence in May.

The tunnel project will be the third passage linking the island of Xiamen with the mainland, joining Xiamen Bridge and Haicang Bridge. The tunnel is expected to divert about 30 per cent of the traffic from the two bridges.