Tiananmen Square – the epicentre of a student pro-democracy protest 20 years ago – has been flooded with armed police and teams of plain-clothed security officials

A virtual lockdown has been put in place to prevent any demonstrations on this most sensitive anniversary.

Foreign television crews have been barred entry to the vast square – and several were detained.

It is thought that more than 2,000 people – mostly students – were killed when the Chinese army put down the protest on June 3 and 4, 1989 – turning tanks and machine guns on the unarmed crowd.

However, the Communist Party has never revealed the precise total of those killed.

The Chinese have now reacted angrily to a call by US Secretary of State Hillery Clinton to publish the names of those killed or missing during the crackdown.