HONG KONG, Feb 9 (Reuters) - Riot police fired warning shots on Tuesday to disperse an angry crowd after clashes erupted when authorities tried to move illegal street vendors from a working-class Hong Kong district, the worst street violence since pro-democracy protests in 2014. Protesters prised bricks from the sidewalk to hurl at police, while others toppled street signs and set fire to rubbish bins in Mong Kok, a gritty neighborhood just across the harbor from the heart of the Asian financial center.