The Hang Seng Index unofficially closed down 0.7 percent at 23,143.23 points. The China Enterprises Index of the leading offshore Chinese listings in Hong Kong fell 0.8 percent.
The head of the Hong Kong stock exchange said on Sunday the stock trading agreement between Hong Kong and Shanghai, hailed as a milestone to open up China's markets to global investors, will not be launched this week as initially expected because it still needed regulatory approvals.
Analysts said the delay had been expected as ongoing pro-democracy protests in Hong Kong had added to market volatililty and alarmed Beijing.
Financials were the biggest losers. CITIC Securities fell 3.5 percent and Haitong Securities dropped 5.2 percent. Bourse operator HK Exchange plunged 4.6 percent.