Beijing: Racing ahead with the construction of the second tallest building in the world, China has completed the foundation for 632-metre high Shanghai Tower, second only to 828-metre tall Burj Khalifa in Dubai.

Work crews have completed the foundation one month ahead of schedule and are now rushing to construct the ground structure of the building situated in China's financial hub of Shanghai.

The building is expected to grow by 400 metres next year, with an average of seven days spent on the construction of each floor, said Kong Qingwei, board chairman of the development firm Shanghai Tower Construction and Development Co Ltd.

Kong said on Wednesday that it took three years to complete the foundation, and estimated that it will take another three to finish the ground structure.

Once completed, the Shanghai Tower will be the tallest structure in China, as well as a new Shanghai landmark alongside the 420.5-metre Jin Mao Tower and the 492-metre Shanghai World Financial Centre.

The three skyscrapers in Shanghai's Lujiazui Financial Zone will be connected by subways.

Kong said the Shanghai Tower will be a "vertical city" as it will house hotels, offices, malls and other facilities and will be capable of holding more than 50,000 people.