Shanghai's housing market had its best half since 2011 in the first six months of this year, with revenues up more than 50 percent year-on-year in terms of floor space, a property consultancy in the city said.

Selling prices were up 5 percent half-on-half to an average of 23,482 yuan ($3,829) per sq m, data from ToSpur show.

ToSpur did not provide year-on-year price comparisons.

The consultancy said 6.05 million sq m of residential property changed hands in the first half, up 9 percent from the second half of 2012 and 57 percent from a year earlier.

Transactions of pre-owned homes also surged on recovering demand, and 144,000 units changed hands from January to May, up 144.7 percent year-on-year.

Despite the robust first-half performance, analysts are cautious about the second-half outlook.

"Soaring trade in March contributed a lot to the total transaction figures. Homebuyers flocked to property agencies to sign deals before the execution of new tightening policies that involve up to 20 percent of the gains from selling a pre-owned property," said Song Huiyong, director of the research and consultation department at the property consultancy Shanghai Centaline.

In March alone, as many as 68,000 units were traded in the secondary market in Shanghai, more than triple the average of 20,000 units for most months, Song said.

"It is these anxious homebuyers who helped drive up prices, and the price rise in turn persuaded more people to abandon their long-held wait-and-see stance," said Lu Qilin, research director at Shanghai Deovolente Realty Co.

A total of 292,000 sq m of apartments priced above 10 million yuan each had been sold across the city as of June 23, up 17.3 percent year-on-year. The average transaction price declined 6.6 percent compared with the same period of 2012, said Wu Huimin, head of residential agency DTZ East China.

Analysts said the property boom probably won't persist in the second half.

"Homebuyers are less motivated. In addition, prices are rising," said Lu.

Another policy uncertainty may emerge in November, when the central government is likely to provide support for the growth of third- and fourth-tier cities as part of the new urbanization campaign.

"The roll-out of favorable policies for smaller cities will mean the government is shifting its attention from first-tier cities like Shanghai, which may jack up demand in smaller cities' property markets," said Song.

Signs of a cooling-down have already emerged. In June, only 8.89 million sq m of newly built residential spaces were traded across China's 20 major cities, down 11.2 percent year-on-year and down 3.3 percent month-on-month, according to figures from the Shanghai-based E-house China R&D Institute.