The day before a gala celebration marking China's National Day was held in Canberra last week, organisers found dozens of posters they had put up at the Australian National University to promote the event defaced with fluorescent green paint.

In large Chinese characters, vandals had smeared the words "Tiananmen Students" along with the numbers "six" and "four", a reference to the Communist Party's darkest of stains: peaceful, student-led pro-democracy demonstrations at Tiananmen Square suppressed in a hail of gunfire and bloodshed on June 4, 1989.

As a crowd of bemused onlookers gathered, the event's incensed organisers, from the university's Chinese Students and Scholars Association (CSSA), hastily tore down the defaced posters.

A Chinese student at ANU, Erica Zhao, said, "It's quite cowardly to vandalise the posters behind people's backs," adding, "Australia is a place for free speech. If they felt bad about the posters they could have just spoken out rather than play tricks.