The world's first museum dedicated to China's Tiananmen Square crackdown is to close its doors in Hong Kong, with organisers saying they believe they are being targeted for political reasons.

It comes at a time when concerns are growing in the semi-autonomous Chinese city that Beijing is tightening its grip.

There has been keen interest in the museum from mainland tourists. Half of the more than 20,000 total visitors since it launched in 2014 have come from mainland China, where all reference to the 1989 military crackdown on pro-democracy protesters is banned.

The June 4 Memorial Hall is run by the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, which also organises the city's huge Tiananmen anniversary vigil each year.

Tenants in the commercial building housing the museum say it breaches regulations because the premises should only be used for offices, according to legal documents seen by AFP.

"I tend to believe they are politically motivated... the other side seem to have unlimited resources," said lawmaker Albert Ho, chairman of the Alliance.

Museum organisers say they cannot afford to continue the protracted legal battle -- the tenants have been pursuing the issue since it first opened.

The current venue will close by year-end and organisers are seeking bigger premises. If they fail to find somewhere in time, the exhibits will be put in storage.

Multiple requests for an interview with tenants' committee officials went unanswered.

One tenant complained to AFP that visitors to the museum "jammed" elevators during peak hours, but others said they were not aware of a public museum in their building.

The crackdown in Beijing's Tiananmen Square on June 4, 1989, is branded a "counter-revolutionary rebellion" by Chinese authorities and many on the mainland remain unaware of it.

Pro-Beijing groups protested when the museum first opened, saying it presented a skewed version of events.

Venue organisers claim visitors have felt "harassed" by security guards who ask them to present their personal information.

The 800-square-foot (74 sq m) museum is in the commercial district of East Tsim Sha Tsui and features video clips and photographs.

There is also a two-metre tall statue of the Goddess of Democracy, similar to one erected at Tiananmen Square during the protests.

Beijing has never given an official death toll for the Tiananmen crackdown, which was condemned worldwide, but independent observers tallied more than 1,000 dead.

Hong Kong enjoys freedoms unseen on the mainland, enshrined in a deal made before Britain handed it back to China in 1997. But there are growing fears those freedoms are being eroded.