The first underwater tunnel in South Asia — the first large-diameter underwater tunnel undertaken by a Chinese company overseas — opened in Bangladesh on Saturday.

Located at the mouth of the Karnaphuli River in Chattogram city, the Bangabandhu Sheikh Mujibur Rahman Tunnel connects the east and west banks of the Karnaphuli River. It is 9.3 kilometers long, has four lanes and is designed for speeds of 80 kilometers per hour.

The tunnel was built by China Communications Construction Company.

Major technical difficulties in construction had to be overcome, such as geological structures. To solve the problems, the project team applied the world's largest steel casing, which allowed specialized machinery to enter and exit the tunnel.

The project, which was designed to Chinese standards, built using Chinese equipment and managed by Chinese enterprises, was hailed as a successful exploration of China's complete industrial chain for the construction of tunnels overseas, and will become a shining business card abroad, according to the company.

As part of the Bangladesh-China-India-Myanmar Economic Corridor, the tunnel is an important link in the Belt and Road Initiative. It will not only greatly improve transportation conditions in Chattogram but will also drive economic development in Bangladesh.

Moreover, it improves the Asian highway network, promotes connectivity between Bangladesh and neighboring countries and will encourage the internationalization of Bangladesh's development, the company said.