The towers of Disney's planned Magic Kingdom in Shanghai are wreathed in scaffolding and mystery after the US entertainment giant pushed back the opening of its first mainland China theme park to 2016.

On a tightly-guarded, 3.9-square-kilometre site east of China's commercial hub, a grey turret of the unfinished "Enchanted Storybook Castle" rises into the sky.

There is no Disney branding at the main entrance, only a sign reading: "Shanghai International Tourism and Resort Zone".

It was originally due to be transformed in time to open this year, but Disney chairman and chief executive Bob Iger last week announced a delay, pushing the opening back to next spring.

He attributed the change to an expansion in the park's size and number of attractions.

"The artistry, complexity, the magnitude and the detail, it's all quite astonishing," Iger said, calling the facility "spectacular".

But Shanghai authorities have not confirmed any plans to expand the project, and people familiar with it point to it following stricter environmental and labour standards than normal in China.

The studios of Hollywood are competing not just for screen eyeballs in China -- whose 1.37 billion people generate the second-largest annual box office in the world -- but also theme park visitors.

The Shanghai Disney Resort will be the company's third in Asia after Tokyo and Hong Kong. But its park in the former British colony can only partly serve the Chinese market, while Universal Studios and DreamWorks Animation are planning rival attractions on the mainland.

For Shanghai, the park represents the city's tourism future following the World Expo in 2010.

One Chinese academic estimates it will contribute $3.3 billion to Shanghai's economy every year and account for one percent of the city's annual gross domestic product.

- It's off to work we go -

Disney and its Chinese partner, state-backed Shanghai Shendi Group, broke ground on the park in April 2011.

Chinese construction is normally staggeringly fast, with towering skyscrapers and multi-lane highways changing urban landscapes at extraordinary pace.

But a Shanghai official told AFP that said one delay arose after contaminated soil on the site failed to meet environmental standards, prompting Disney to bring in a foreign contractor to remedy the problem. Workers removed topsoil up to a metre deep.

A worker said that the builders were insisting on a standard eight-hour work day, preventing faster construction -- unlike many other sites in China where labour laws are loosely enforced and routinely violated.

Disney did not respond to a request for comment on the delay.

As well as its Asian properties, the firm also has parks in the US states of California and Florida and near the French capital Paris -- where there was outrage over the prospect of American cultural invasion when it was first proposed.

The Shanghai government is promising to finish a metro line extension linking to the park and other infrastructure this year.

But city fathers also have another issue in mind after 36 people were killed in a stampede during New Year's Eve celebrations.

"Management of the Disney Resort's huge flow of people is an extremely important issue," Shanghai mayor Yang Xiong told reporters last month. "We believe Disney has a lot of experience, but we should also do our part to make full preparations."

- To infinity and beyond -

With the opening of its first resort in mainland China, Disney is banking on Chinese parents willing to spend lavishly on their children and a rising middle class intent on travel.

It has not announced prices for Shanghai, but an adult one-day ticket at the Hong Kong park costs $65, nearly a quarter of China's average monthly disposable income last year.

When the $5.5 billion Shanghai facility opens, it will boast the biggest Disney castle in the world, a production of "The Lion King" in Chinese and a pirate-themed zone based on the movie franchise "Pirates of the Caribbean".

An artificial mountain will loom over the park, becoming the highest hill in Shanghai's Pudong district, and a 420-room Disneyland Hotel is planned in an "elegant Art Nouveau style", with another based on the "Toy Story" films.

On a commercial level, an adjacent "Disneytown" will have 46,000 square metres (495,000 square feet) of shops, restaurants and a 1,200-seat theatre.

He Jianmin of the Shanghai University of Finance and Economics, who has consulted for the city on the tourism zone, forecast the park will initially attract seven million visitors a year, eventually rising to 16 million.

"China's tourism industry was neglected before for all sorts of reasons, like income not reaching a certain level," he said.

"Earlier the emphasis was on manufacturing. After the Shanghai Disney park becomes completely mature, it will be a new format for China."

But a site worker sweeping a street said he might not share in the excitement after the park opens.

"The Disney park will definitely be fun, but I don't know if I will go," he said. "I don't know how much tickets will cost."