Pan told China Daily that at the moment, five floors from the 68th to the 72nd have sold out, each priced between 82,000 yuan and 83,000 yuan per square meter (sq m). The only identified buyer so far is Tomson Group, a property developer founded in Taiwan but which manages most of its assets in Shanghai. Tomson acquired the 72nd floor of SWFC, roughly 3,221.87 sq m of gross floor area, for 267 million yuan.

Considering the total cost to build the skyscraper was 8.3 billion yuan, Mori Building only needs to sell less than half of its office floors to make ends meet, said Lu Qilin, a research director from Shanghai-based real estate agency Shanghai Deovolente Realty.

The 492-meter-high skyscraper has been plagued with a high vacancy rate since clients began to be canvassed after completion in August 2008. After readjusting its strategy, the company behind the iconic building raised the occupancy rate to above 80 percent and strengthened its capital flow as well, according to Mori Building China (Shanghai).

Andy Zhang, managing director of Cushman & Wakefield China, said despite the growing percentage of foreign investors in China's commercial property market, there are still quota restrictions on their investment scale.

"Currently, private equity and funds are the main players in investing in China's commercial properties. However, due to their special requirements for properties, there are not many qualified projects," said Zhang.

According to him, most of the foreign funds and private equities look for projects costing several hundred million US dollars with high quality management.

Even if the investors are willing to make a deal, overseas investors have to wait for a much longer approval time than local rivals. In some cases, the waiting time can extend to 10 months, Zhang added.

"It is more difficult for us to make an investment in the mainland market now," said a managing director at a leading US real estate fund, who declined to be named.

"On one hand, banks have tightened loans to the realty sector. On the other hand, the approval process of a foreign real estate investment will nearly drive everybody crazy," he said.

Currently, foreign investors are more interested in transparent markets in Shanghai and Beijing, but the rapid growth of the second-tier cities of Chengdu and Chongqing make them also premium choices, Zhang said.

Wu Tao, managing director of Wins Investment Management Co Ltd, said its fund will explore investment opportunities in the commercial sector in the near future. The company, which is totally owned by Gemdale, a leading property developer based in Shenzhen, currently manages a joint venture real estate fund with UBS and a yuan-denominated fund.

"The yield of an investment in a commercial property project largely depends on the fund's operating and management capacities," said Wu. "An annualized return of 10 to 15 percent will be quite satisfactory for a commercial property investment, compared with a 20 to 30 percent return from a residential development.

Domestic players who traditionally focus on the residential sector also sense good returns in the commercial real estate especially after the central government showed its determination to cool the residential market.

Cushman & Wakefield predicts that as the restriction continues in the residential sector, more domestic and foreign investors will pour into commercial real estate. A growing economy will bring about more opportunities for office leasing and trading, most investors believe.

During the latest fiscal year report, major Chinese developers China Vanke Co, Poly Real Estate Group Co Ltd and Gemdale Co sent clear messages that they were ready to develop commercial properties. Beijing-based SOHO China Ltd has purchased seven commercial projects in Shanghai since 2009.

However, the oversupply of commercial properties is also looming on the horizon, experts warn. "There is a saying that the bubble in commercial properties is even bigger than that in the residential market. Although I cannot confirm the saying, the lavish spending on commercial properties may pose a threat to the investors' portfolios, too," Zhang noted.

The development of commercial properties should match the pace of the economy, and it's necessary to monitor any investment risk, Yang said.

Hu Yuanyuan in Beijing contributed to this story.