U.S. stocks tumble, extending last week's steep losses
U.S. stocks closed sharply lower Thursday, extending last week's steep losses.
Hong Kong stocks open 0.83 pct higher
Hong Kong stocks gained 212.40 points, or 0.83 percent, to open at 25,674.66 points on Thursday.
U.S.-listed Chinese firms trade mostly lower
Shares of JD.com and TAL Education Group slid 3.86 percent and 2.15 percent, respectively.