China is reportedly planning to construct an undersea railway tunnel to operate high-speed bullet trains, in a bid to connect Beijing with all of the provincial capitals in the country.

The proposed 5,700km-long undersea railway tunnel is likely to run through the Bohai Gulf, connecting north-east China and South China’s Hainan Province.

The state-run Global Times reported that it will connect Beijing with the provincial capitals with a travel time of eight hours.

"The tunnel will connect Beijing with the provincial capitals with a travel time of eight hours."

China is currently seeking private investments in the rail sector as its development will stabilise economic growth, enhance social harmony and help urbanisation.

Beijing Jiaotong University School of Economics and Management professor Zhao Jian said: "It is internationally believed that a distance of 500km is to the best advantage of high-speed railways and a distance of 1,000km is the maximum, but the distances between big Chinese cities are usually more than 1,000km.

"There are more trains between Beijing and Jinan along the line, at a distance of around 500km than between Beijing and Shanghai, while the number of flights between the two biggest metropolises in China has not decreased."