Thirteen Hong Kong universities and academic institutions accused the Chinese-ruled city's leader of undermining freedom of expression amid a row over pro-independence banners appearing on campuses.
Hong Kong, a former British colony that returned to China in 1997, is guaranteed freedoms and a high degree of autonomy under a "one country, two systems" arrangement, including freedom of expression.
At the start of the academic year, banners advocating independence from China appeared on notice boards in at least seven universities. Some large black banners were hung across buildings.