Work on the main structure of the world's second tallest skyscraper was completed on Saturday, as the final beam was placed on the Shanghai Tower.

A crane placed the steel beam 580 meters (1,900 feet) above the ground in Shanghai, China's commercial hub, as the building formally overtook Taiwan's 509 meter tall Taipei 101 building to become the highest tower in Asia.

Globally it is second only to the Burj Khalifa in Dubai, which stands at 830 meters. The tower, which costs an estimated $14.8 billion yuan ($2.4 billion), will reach over 630 meters when it is finally finished.

"It's a landmark and it will change the skyline of Shanghai," Xia Jun, of Gensler, the US firm which designed the tower, told a press conference on Saturday following a "topping out" ceremony.

"I don't think the importance of an architecture lies entirely in its height," he added.

The structure stands alongside China's previous tallest building, the 492 meter Shanghai World Financial Center -- and is due to open next year, by which time it may have been surpassed as the tallest building in China.

Chinese firm Broad Group have announced plans to construct an 838 meter tower in the central Chinese city of Changsha, which they say will be completed in April.

But reports in state-run media late last month said construction on the tower had been called off, because the building had not gained full local government approval.

The Broad Group called the reports inaccurate and said they had not been asked to halt construction in a statement sent to AFP this week.

Work on the Shanghai tower began in 2008, and its construction was partially backed by Shanghai's city government.

Concerns were raised last year when long cracks began to appear in the ground close to the building, prompting fears that ground around the tower was subsiding.

But Ding Jiemin, an architect who collaborated on the tower's design, played down fears on Saturday.

"These problems were just during construction period, it will not affect the security of the architecture," he said.

China is home to three of the world's 10 tallest buildings, according to research group Emporis -- which did not count the Shanghai Tower.

The Shanghai Tower's final beam was decorated with red ribbons and flags, and carried a banner which read: "Team of hoisting heroes".