** Shares of Hang Seng Bank 0011.HK drop 6.9% to HK$114.40, their lowest level since June 24

** Stock set for the biggest one-day pct decline since April 7

** Top pct loser on Hang Seng Finance Index .HSNF and Hang Seng Composite Index tracking financials stocks .HSCIF, both down 1%

** The bank, in which HSBC 0005.HK has majority ownership, says its first-half profit attributable to shareholders down 30% y/y to HK$6.88 bln ($876.46 mln)

** Benchmark Hang Seng Index .HSI down 0.6%

** YTD, stock up 21%

($1 = 7.8498 Hong Kong dollars)

(Reporting by Donny Kwok)

((donny.kwok@thomsonreuters.com))