SHANGHAI, Sept 28, 2007 (AFP) - China has announced another package of measures to cool the country's red-hot property market, including raising the the downpayment requirement for second homes to 40 percent.

"Domestic property prices are rising quite fast and there are obviously irrational factors behind this," the central bank and the China Banking Regulatory Commission said in a joint statement released late Thursday.

The statement said commercial banks were facing "significantly higher risks" and if property prices became too volatile, a surge in bad loans was likely to follow.

As part of the new measures, which take effect immediately, the downpayment requirement for people buying a second home was raised to 40 percent from 30 percent.

The downpayment required for commercial properties such as offices was also raised to 50 percent from 40 percent.

Further, mortgage rates for second homes and commercial properties must now be at least 1.1 times the benchmark lending rate, the statement said. Previously the minimum was equal to the benchmark rate.

The statement said banks were banned from providing loans to developers that had been found hoarding land or houses, and that real estate vacant for more than three years must not be accepted as collateral for bank loans.

China has since 2005 taken many steps, including interest rate hikes and imposing taxes, to curb rapidly rising real estate prices amid concerns of a dangerous bubble in the sector.

Interest rates have been hiked five times this year alone, most recently on September 15, with apparent little effect.

Property prices in 70 major cities across the country rose 8.2 percent in August from a year earlier, the fastest so far this year, according to official data.

Property prices in Beijing were up 12.1 percent in August year-on-year and 20.8 percent in southern Shenzhen, a booming city just across the border from Hong Kong.