Commercial housing sales in Beijing fell 12 percent year-on-year in the first three quarters of the year, a sign that the red-hot property market has begun to cool down, the municipal statistics bureau said Monday.

The total area of commercial housing sold slumped to 6.32 million square meters during the January-September period, the Beijing statistics bureau said in a press release.

Prices of new homes in the city have shown zero month-on-month growth for four straight months, while prices of pre-owned homes fell 0.4 percent month-on-month in September, according to the National Statistics Bureau.

The slump has been attributed to the government's tightening measures, which include higher mortgage rates, a ban on third-home mortgage loans and purchase restrictions.

However, sales of affordable housing for low-income earners jumped to 1.98 million square meters during the January-September period, up 120 percent year-on-year, the press release said.

Construction began on 13.75 million square meters of affordable housing during the nine-month period, up 470 percent year-on-year, as the city government has been building more such housing to help tame high housing prices.