Hong Kong monetary chief Norman Chan said more measures are possible to cool the city's housing market as elevated household debt adds to risks from property-price gains over the past four years.

Debt is "near historic high levels," Chan, the chief executive of the Hong Kong Monetary Authority, said yesterday, citing ratios of 58 percent to 59 percent of gross domestic product in the third and fourth quarters. In a housing and economic downturn, repayment may become more difficult, he said.

Chan said the HKMA can roll out a sixth package of measures if necessary to rein in the property market after already using tools such as limits on mortgage terms. In October, the government added a tax on foreigners' home purchases. Overheating in the housing market is the biggest risk to financial stability, Chan said, echoing a warning in December from the International Monetary Fund.

"If one believes that the housing market and the economy go in cycles," household debt levels may rise further when a downturn comes, Chan said. That's because "the economy will become more difficult and personal and household income will be negatively affected," he said.

Household debt in Hong Kong almost doubled to HK$1.21 trillion (US$156 billion) last year from HK$662.8 billion in 1997, when the housing bubble in the city burst, according to the HKMA. Mortgage loans of households jumped 64 percent to HK$888.9 billion during the period, while credit card and personal loans increased almost three-fold to HK$320.1 billion, the data show.

Home prices have doubled since the start of 2009, according to a weekly index compiled by Centaline Property Agency Ltd.

The IMF said that the city's property sector was the main source of domestic economic risk. At the same time, the odds of a slump that has major economic and financial consequences is "fairly low in the near term," the IMF said in December.