Hong Kong protests: up to 800 trapped as police lay siege to university
Tear gas stops protesters escaping despite president of Polytechnic University assuring them of safe passage
Hong Kong police have trapped up to 800 people inside a university in the city, firing tear gas at any protesters trying to escape the campus.
Polytechnic University, a sprawling campus that has been occupied by protesters since last week, has become the site of the most prolonged and tense confrontation between police and demonstrators in more than five months of political unrest.