** Shares of Sunac China Holdings plunge 21.4% to HK$2.42, on track for biggest one-day pct drop since Oct 8 if current losses hold

** Stock top pct decliner on index tracking property and construction stocks , which is down 0.2%; third biggest pct loser on the Hong Kong bourse

** Chinese property developer plans to sell 489 mln new shares to key shareholder Sunac International, raising HK$1.21 bln ($155.68 mln) to support long-term solutions for its onshore corporate bonds and for working capital

** New shares will be sold at HK$2.465 apiece, representing a 19.97% discount to Wednesday's close of HK$3.08

** Sunac International will buy the new shares following sale of same amount of existing shares at same price to third party investors

** The Hang Seng Mainland Properties Index falls 1.1%, while the Hang Seng Index rises 1.8%

** Sunac shares up 70% YTD

($1 = 7.7726 Hong Kong dollars)

(Reporting by Donny Kwok)

((donny.kwok@thomsonreuters.com))