A Chinese man stands alone to block a line of tanks heading east on Beijing's Cangan Blvd. in Tiananmen Square on June 5, 1989. Pic: AP.

BEIJING (AP) — Beijing has launched a security crackdown on the eve of the 25th anniversary of the crushing of pro-democracy protests centered on the capital’s Tiananmen Square.

Police manned checkpoints on Tuesday and officers along with paramilitary troops patrolled over pedestrian overpasses and streets surrounding the square in the city center.

The increased security comes on top of heightened restrictions on political activists, lawyers and other government critics. Dozens have been taken into detention, forced out of Beijing or confined to their homes in other parts of the country.

China allows no discussion of the events of June 3-4, 1989, when soldiers accompanied by tanks and armored personnel carriers fought their way into the heart of the city, killing hundreds of protesting citizens and onlookers.