Taiwan's president on Sunday offered to help China to transition to democracy, on the 28th anniversary of China's bloody crackdown on pro-democracy protests in and around Beijing's Tiananmen Square, as thousands gathered in Hong Kong for an evening vigil.

Nearly three decades after Beijing sent tanks and troops to quell the 1989 pro-democracy, student-led protests, Chinese authorities ban any public commemoration of the subject on the mainland and have yet to release an official death toll.

Hong Kong, a former British colony that returned to Chinese rule in 1997, is the only place on Chinese soil where a large-scale commemoration takes place, symbolizing the financial hub's relative freedoms compared with the mainland.