A group of mothers of those killed in the 1989 protests in Tiananmen Square has urged China's leaders to fully investigate the deaths.

Their call was issued as the 20th anniversary of the massacre approaches, and days ahead of the annual session of the National People's Congress.

The Tiananmen Mothers want the government to name the dead, compensate families and punish those responsible.

In an open letter, Chinese leaders were also urged to "break the taboo".

Those involved in China's rights movement say few young people in China know about or understand what happened.

The Tiananmen mothers want the government to seek and reveal the truth behind the decision to send tanks and troops to crush the student-led peaceful protests on 3-4 June 1989, which were seen by the leadership as a threat to Communist Party rule.