A protester raises his umbrellas in front of tear gas which was fired by riot police to disperse protesters in Hong Kong, September 28, 2014.

Unrest in Hong Kong is spooking markets for fear it could escalate, challenging Beijing to make a measured political response, at a time when Chinese and global growth are at the heart of market anxiety.

Worries about soft Chinese growth and European weakness has made investors uneasy, while the U.S. Federal Reserve signals it is moving away from easy policy and getting closer to returning to a more normal interest rate environment as the U.S. economy gets stronger.