The Chinese mainland registered a 12-percent year-on-year increase in its number of millionaires last year, boosted by economic growth and equity market gains, a Capgemini report said Thursday.

The combined wealth of the mainland's 535,000 high net worth individuals (HNWIs) topped 2.66 trillion U.S. dollars, up 13.2 percent from 2009, accoring to a joint report issued by Capegemini and Merrill Lynch Global Wealth Management.

The number of millionaires on the mainland makes the region the second-largest HNWI market in the Asia-Pacific region and the fourth-largest in the world after the United States, Japan and Germany, according to the report.

China is continuing to see an expansion in its HNWI population and their wealth, fueled by strong macroeconomic growth and market performance, particularly in equities and real estate, said Pauline Ko, market manager for China at Merrill Lynch Global Wealth Management.

The mainland's HNWIs had 42 percent of their investments in equities and 27 percent in real estate last year, the report said.

Wei Zhen, Asia strategist with Merrill Lynch (Asia Pacific) Ltd., said that he expects Chinese millionaires to gradually reduce their wealth allocation in the equity and property markets, as the government will not loosen its grip on the real estate market anytime soon and global equity markets may turn volatile.

Wei projected that China's economy will expand by 9.3 percent this year and nine percent in 2012.

The report also said the number of millionaires in Hong Kong reached101,300, up 33.3 percent from 2009, the fastest growth globally for the second consecutive year due to rising asset prices. Their total wealth reached 511 billion U.S. dollars last year, up 35 percent from a year earlier, marking the world's top growth rate, the report said.

The number of HNWIs in the Asia-Pacific region hit 3.3 million last year, replacing Europe for the first time as the world's second-largest HNWI market after North America.

HNWIs are defined as individuals who have investable assets of one million U.S. dollars or more, excluding primary residences, collections, consumables and consumer durables.