Hong Kong protesters shot arrows and hurled petrol bombs from a barricaded university on Sunday at police who fired tear gas and water cannon in some of the worst violence in the Chinese-ruled city since anti-government unrest erupted five months ago. Several protesters took up positions on the rooftops of Hong Kong Polytechnic University, armed with bows and arrows, as unrest spread across the territory's central Kowloon district. Protesters, who were sprayed with the blue liquid from water cannon, stripped off and hosed each other down to wash it off.