Last month, several thousand Hong Kong university students, some of them under the watch of a closed-circuit TV camera, were the first to take compulsory courses on the territory’s national security law.

The content of the courses set out the dangers of breaking the law, in one case demonstrating how a message in a chat group could be interpreted as a serious breach, punishable by up to life in prison.

At Hong Kong Baptist University, at least one closed-circuit TV camera was present in the lecture hall, while an unidentified photographer took pictures, according to two students who attended.