Thousands of real estate agents took to Hong Kong's streets Sunday in protest at government efforts to curb soaring property prices, saying new transaction taxes and other measures are threatening their business.

"There are 37,000 agents in Hong Kong and there were only 3,000 transactions last month," said Raymond Ho, a spokesman for the rally organisers.

"The policies have frozen the market. A lot of small property agent firms will close in the future," he told AFP.

Organisers said 23,000 joined the rally while police put the turnout at 5,500. Protesters chanting slogans marched through the busy Causeway Bay shopping district before assembling at the government headquarters at Admiralty.

Home prices in the crowded city have risen by 120 per cent since 2008, and by more than 30 per cent from their previous peak in 1997.

A 900-square-foot (81 sq metre) apartment in the middle-market Tai Koo Shing estate sold for more than HK$10 million (US$1.29m) last year, after being priced at about HK$3 million in 2003.

Prices in the luxury market have been pushed up by wealthy buyers from mainland China. Hong Kong residents have also been investing in property because the local currency is pegged to the US dollar and bank interest rates are lower than inflation.

Officials say the measures to cool the market, in the form of extra stamp duties on some purchases, are aimed at stemming short-term speculative inflows.

They have so far had little effect in driving down prices but sales have dropped off dramatically.

Shih Wing-ching, co-founder of the Centaline property agency who joined the rally, said the cooling measures hindered property owners from freely selling their investments since the stamp duties discourage potential buyers.

Ho said 90 percent of property agents received no commissions last month and the number of transactions dropped by 70 percent since the cooling measures were introduced.

Housing minister Anthony Cheung stresed on Friday the measures were exceptional, in an apparent attempt to appease growing hostile sentiment from the business sector.

"We still feel that the market could be volatile, so we have to be very careful about any bubble risk," Cheung told reporters. "These measures are exceptional measures under exceptional circumstances."