Concerns are mounting that efforts by governments and central banks to stoke a recovery will create a nasty side effect: asset bubbles in real-estate, stock and currency markets, especially in Asia.

The World Bank warned Tuesday that the sudden reappearance of billions of dollars in investment capital in East Asia is "raising concerns about asset price bubbles" in equity markets across Asia and in real estate in China, Hong Kong, Singapore and Vietnam. Also Tuesday, the International Monetary Fund cited "a risk" that surging Hong Kong asset prices are being driven by a flood of capital "divorced from fundamental forces of supply and demand."

Prices are surging across a host of markets. Gold, up about 44% this year, soared to a record high Tuesday. Copper is up about 50% in the past year. In the U.S., risky assets are rising rapidly in price: The risk spreads, or interest-rate premiums, on low-rated junk bonds have narrowed to about where they were in February 2008, before Bear Stearns and Lehman Brothers fell, according to Barclays Capital.

Policy makers from Beijing to London, seared by the fallout from burst housing and credit bubbles, are searching for ways to head off new ones. How to handle a bubble "is one of the big two or three unanswered questions at the end of this crisis," says Adair Turner, chairman of the U.K.'s Financial Services Authority. Bank of Korea Governor Lee Seong-tae hinted last month he would raise interest rates, if necessary, to prevent Seoul's housing market from lurching out of control.

"This is the beginning of another big and excessive run-up in asset prices," said Simon Johnson, a former IMF chief economist.

Over the summer, a Singapore condominium developer raised prices 5% the day before units went on sale. After dozens of would-be buyers lined up on a steamy night, the developer -- a joint venture of Hong Leong Group and Japan's Mitsui Fudosan -- held a lottery for a chance to bid on the units. Singapore home prices rose 15.8% in the third quarter, the fastest rate in 28 years.

Australian real-estate markets also have heated up. After a Melbourne property-research firm recently predicted that average home prices will double over the next 12 years, a news report in Australia's Herald Sun said: "The staggering prediction shows the importance of buying a home as soon as you can afford it because the longer buyers delay, the more chance there is that their dream will slip out of their reach."

The Australian dollar has jumped about 35% over the past 12 months as investors borrow in U.S. dollars to purchase Australian currency. The practice is propelling stock and bond markets faster than in the U.S. and Europe. Currency traders are betting that the Australian central bank, which raised interest rates by 0.25% on Tuesday, the second rise in two months, will continue tightening.

About $53 billion has gone into emerging-market stock funds this year, according to data collector EPFR Global. Through Monday's trading, the broad MSCI Barra Emerging Markets Index this year was up 60.7%. Brazil was up 100%, and Indonesia had gains of 102.7%. Over the same period, the Dow Jones Industrial Average was up 11.5%.

Discerning a bubble is as difficult as preventing one. Rapidly rising prices aren't definitive proof. Stocks in Asian emerging markets currently trade at about two times book value, about average for the past 20 years, according to UBS. From 2004 to 2008, the price-to-book-value average was about three times. "This doesn't feel like a bubble," said Hugh Simon, chief executive of Hamon Investment Group, which manages Asia-investment funds. "There's too much skepticism" among investors.

To battle bubbles, policy makers are turning first to regulation. Singapore's authorities tightened mortgage requirements, ended real-estate stimulus policies and pledged to make more land available for development. South Korea regulators tightened real-estate lending requirements in seven districts around Seoul where prices have jumped.

"Even those who say we should respond directly [and deflate bubbles] have no idea how to do it," said Laurence Meyer, a former Fed governor. "It is easy to take a philosophical position, but hard to become operational and practical about it."