Investors looking for new places to park their cash in Hong Kong are driving up prices for parking spaces, sparking fears of a bubble in the Asian financial center.

Prices for parking spots in Hong Kong are nearing historic highs, the side effect of government curbs to cool the housing market amid worries of overheating following the latest round of monetary stimulus in the U.S. last month.

There are "a lot of speculators in the market, especially for car parks," said Buggle Lau, senior analyst with Midland Realty. A bubble is "definitely forming."

Over the weekend, a developer sold about 500 parking spots at a new suburban apartment complex at prices of up to 1.3 million Hong Kong dollars ($167,000) per space.

In a commercial building near the city's financial district on Hong Kong Island, an investor has put 34 parking spaces on sale for HK$100 million ($12.9 million), according to a report last week in the Ming Pao newspaper. A parking spot in the exclusive Repulse Bay neighborhood sold for HK$3 million, the paper also said, citing Land Registry data.

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    On Thursday, a single parking spot in a building in the popular Mid-Levels residential neighborhood will be auctioned off with the opening bid at HK$680,000.

    Second-hand parking spaces changed hands in the third quarter for an average of HK$640,000. That's up 16.4 percent over the year before, according to research by property company Centaline. It's also not far off the record HK$660,000 in the fourth quarter of 1997, shortly before the city's property market collapsed.

    Parking — and other real estate — in Hong Kong is expensive because both steep hills and past government policy to keep land supply tight means there is limited space to build on. Car ownership levels are relatively low but so are the number of parking spaces. The city has 443,442 private cars and 479,000 private parking spaces, according to government data.

    Parking prices are now rivaling housing prices. A three-bedroom, 1,030 square foot (96 square meter) apartment at the new Festival City development in Tai Wai district, where the 500 parking spots went on sale, was sold earlier this month for HK$8 million, or HK$7,767 per square foot. Based on a typical size of 150 square feet, the HK$1.3 million parking spot would cost HK$8,667 per square foot.

    The rising prices are a side effect of recent measures to cool Hong Kong's housing prices, which have doubled since the end of 2009 and are among the highest in the world.

    Hong Kong's government has introduced three separate sets of measures since the summer aimed at cooling the market, including speeding up the release of more affordable housing and tightening mortgage requirements. The latest measures announced in October include a new tax on foreigners and higher stamp duty on investors flipping properties.

    They come in response to efforts by U.S. policymakers to stimulate the American economy by keeping interest rates low. Hong Kong leaders are worried that investors turned off by U.S. investments with unattractive interest rates will pour their money into the southern Chinese city, pushing asset prices higher as investors chase profits in the property market.

    The latest curbs don't cover nonresidential properties such as parking spots so investors have been piling in as they look for higher returns. Hong Kong had the world's third-highest monthly parking charges last year, according to real estate company Colliers International.

    "In some car parks, especially in urban areas where supply is limited, the sales price of some car parks can be as high as 2 to 3 million (Hong Kong) dollars" each, said Lau of Midland Realty.

    Nearly 8,400 parking spaces worth HK$5.6 billion changed hands in the first 10 months of this year, compared to 8,300 such transactions worth HK$5.4 billion for all of 2011, according to Land Registry data compiled by Midland.

    Some of that increase comes from developers like Cheung Kong Holdings, Sun Hung Kai Properties and Chinachem Group selling off parking spaces at their apartment complexes. It's a break from the usual practice of renting them out to residents, and is a sign that the developers realize it's a "pretty good time" to sell because of the prices they can get, Lau said.

    Because Hong Kong's currency is pegged to the U.S. dollar, policymakers cannot take conventional measures to cool property prices like raising interest rates.

    So the government tightened restrictions on property purchases, including bringing in a new stamp duty on foreign buyers. But parking spots and other non-residential property are exempt.

    "The latest overseas buyers' stamp duty will just put some fuel onto that fire, and is making the whole parking space investment market go out of control," said Josh Wong, whose Hong Kong City Parking owns about 200 parking spots at eight lots around Hong Kong.

    Many investors who buy spaces rent them out to car owners. Wong said he typically looks for an annual yield, or return, of 5 to 6 percent, but because prices have risen, yields have been falling to about 4 to 5 percent. He said has even heard of investors making as little as 1.8 percent on their investment.

    Wong, who also runs Parkinghk.com, a website for buyers and sellers of parking spots, said the market was heating up because investors didn't need a lot of money to get started.

    "One million Hong Kong dollars ($129,000) cannot buy anything in Hong Kong. You cannot buy a shop, you cannot buy anything except car parking and that would help the car park investment go even more crazy," he said.