cnn's anna corryn is live in hong kong. what's the latest? >> reporter: we are several blocks from the university where hundreds of those protesters are trapped inside. police have blocked all entrances and exits and say that everybody inside has to surrender and will be arrested. but they are digging in. here you've got protesters on the streets throwing petrol bombs. we were chased a short time ago by riot police firing tear gas. the water cannons also kroef past. we're expecting them to come past. but this is seen as a diversion protest, if you like. this is not only such a busy shopping district, there are thousands of people who have taken to the streets. they are furious that their comrades, their brothers and sisters are trapped inside this