Why Hong Kong students are boycotting Tiananmen vigil

Hong Kong is gearing up to commemorate the anniversary of the 1989 Tiananmen Square crackdown on 4 June.

It is the only city on Chinese soil where such a public event is allowed.

In mainland China, activists have been moved or put under house arrest to prevent them from marking the date.

This year, the candlelight vigil in Hong Kong has been touched by controversy.

For the first time, a key pro-democracy group, the Hong Kong Federation of Students, will not be taking part, though some of its members will attend as individuals.

BBC News examines the background to the rift.

Produced by Juliana Liu