The Foreign Correspondents' Club of China (FCCC) said it had received at least three reports of authorities blocking reporting at Tiananmen Square and intimidating journalists or their sources.
The country's communist leadership sent soldiers to forcibly clear the square and surrounding areas on the night of June 3-4, 1989, ending seven weeks of protests calling for political reforms.
Hundreds, possibly thousands, were killed in the crackdown, which remains a taboo subject in China.