* HSI -1.5 pct, H-shares -1.1 pct, CSI300 -1.0 pct
* PMI contraction triggers across-board HK selloff
* Mainland and Hong Kong property down on Vanke comments leak
By Natalie Thomas
BEIJING, May 5 (Reuters) - Hong Kong shares were down sharply on Monday after a private survey showed mainland manufacturing contracting for a fourth straight month, triggering a selloff across the board.
Mainland shares also fell, with property counters an added drag after leaked comments from a top real estate executive spread pessimism in the industry, though overall losses were partly mitigated by gains in rail stocks.
By midday, the Hang Seng Index was down 1.5 percent at 21,917.39 points. The China Enterprises Index of the top Chinese listings in Hong Kong dropped 1.1 percent.
The CSI300 index of the largest Shanghai and Shenzhen A-share listings was down 1.0 percent, while the Shanghai Composite Index was down 0.7 percent at 2011.54 points.
The HSBC/Markit purchasing managers' index (PMI) for April came in at 48.1 on Monday, lower than a preliminary reading of 48.3, though was up slightly from an eight-month low of 48.0 in March.
"From a technical point of view Hong Kong is still in a correction mode," said Jackson Wong, Tanrich Securities' vice-president for equity sales.
He added that while last week the index had managed to stave off major losses, the fact that the PMI numbers came in below expectations meant a selloff was unavoidable.
"This week I would say around 21,500 would provide pretty good support. However, the technicals are still very negative."
Property stocks took a heavy hit on both exchanges, after private comments made by a top executive from the mainland's largest listed developer showing scant optimism for the health of the sector were leaked to the press over the holiday weekend.
Speaking at a dinner, Mao Daqing, Vice-chairman of China Vanke Co Ltd, compared China's current situation to that of Japan and Hong Kong right before their property bubbles burst.
Investor nerves were not helped by Chinese media reports on Monday that 32.5 percent fewer houses were sold during the long weekend in China's 54 major cities compared with a year ago.
The CSI300 real estate index was down 2.1 percent, with Vanke losing 1.7 percent and Poly Real Estate Group Co Ltd down 3.4 percent.
Losses were similar in Hong Kong, Cheung Kong Holdings Ltd slid 2.5 percent, while Wharf Holdings Ltd dropped 4.1 percent.
One of the few bright spots came from mainland-listed rail shares, which gained on reports last week that the country's 2014 railway investment would be increased to 800 billion yuan ($128 billion) from 720 billion yuan.
China Railway Group Ltd gained 2.8 percent, China Railway Erju Co Ltd was up 2.2 and China Railway Construction Corp Ltd jumped 2.1 percent. ($1 = 6.2593 Chinese Yuan) (Editing by Eric Meijer)