BEIJING, June 11 -- Investment growth in China's property sector continued to slow in the first five months of the year, while sales volume of commercial housing increased, official data showed on Thursday.

Investment in the property sector rose 5.1 percent year on year to 3.23 trillion yuan (528.21 billion U.S. dollars) from January to May, the National Bureau of Statistics (NBS) announced.

The growth narrowed from the 6-percent increase seen in the first four months, underscoring lingering weakness in the sector.

China's property market took a downturn in 2014 under the accumulative effects of measures to curb the overheated sector. The cooling trend has continued into 2015, with both sales and prices falling, and investment slowing.

In the January-May period, investment in residential housing posted an increase of 2.9 percent from the same period last year to 2.16 trillion yuan, down from the 3.7-percent growth registered in the first four months.

Sales volume of commercial housing rose 3.1 percent year on year to 2.44 trillion yuan in the first five months, a decline of 3.1 percent was also posted for the first four months.

The total floor area of sold commercial housing reached 359.96 million square meters by the end of the first five months, down 0.2 percent from the previous year. The drop narrowed the 4.8-percent decline registered for January to April.

Sales of commercial housing have picked up recently, with home prices in bigger cities posting obvious growth, said NBS senior analyst Wang Baobin. Market expectations have improved and home buyers' confidence has strengthened, thanks to a string of easing policies, Wang said.

The central government has announced a series of supportive measures this year, including lower down payments and tax exemption for some home purchases.

The central bank has cut the benchmark interest rates three times since November. The reserve requirement ratio (RRR), the amount of cash banks are required to hold as reserves, has also been cut twice this year.