By Clare Baldwin

HONG KONG (Reuters) - China's only museum commemorating the 1989 crackdown on protesters in Beijing's Tiananmen Square is to close temporarily after a long-running legal battle with the management and owners of the building it is housed in.

The museum opened in April 2014. Unlike in mainland China where the 1989 crackdown on student-led protests remains taboo, the museum - and an annual candlelight vigil attended by tens of thousands every year - is legal in Hong Kong.

The June 4 museum is run by a group called the Hong Kong Alliance in Support of Patriotic Democratic Movements in China. Soon after it opened, owners of the building it is housed in brought a lawsuit against the alliance saying the museum violated the deed and occupation permit, an entertainment ordinance and fire safety codes.

The museum was a "nuisance" and had caused a "loss of privacy" as well as security concerns that "necessitated more security staff to be hired", said the chairman of the owners' incorporation, Chau Kwok Chiu, according to Hong Kong public court filings dated Feb. 16, 2015.

Building security guards also began asking museum visitors to register their names and identity card details and imposing limits on the number of people per floor at any time, in line with instructions in a notice to building occupants from the owners, seen by Reuters.

Lawyers for the building's owners' incorporation and Chau did not respond requests for comment.

The liaison office of the Chinese government in Hong Kong was not immediately available for comment. A Chinese foreign ministry spokesman in Beijing referred queries to the government's Hong Kong liaison office.

The decision to close the museum comes amid broad concern about what activists see as growing restrictions on Hong Kong's freedoms under a "one country, two systems" framework under which Beijing governs the former British colony.

Lee Cheuk-yan, a city lawmaker who has long been involved with the Hong Kong Alliance in Support of Patriotic Democratic Movements, said after two years, the museum had decided it was a waste of money to keep fighting the lawsuit.

He said the insistence of the building's guards to record visitors' ID numbers and limit the number of visitors had become such a problem it was better to close and relocate.

Lee said he suspected political pressure from Beijing's supporters was behind the museum's difficulties, though he acknowledged there was no proof of that.

"It's quite sad in a way that we have to close down temporarily," Lee said. "This should not happen in Hong Kong. We are supposed to be free."

Museum exhibits include photographs and video clips from the Beijing protest, a signed Peking University T-shirt, books, and other memorabilia.

About 24,000 people have visited since it opened, Lee said.

Albert Ho, another lawmaker involved with the museum, said they hoped to re-open within a year but they had yet to find a venue.

China has never released a death toll from the crackdown after troops cleared protesters from central Beijing. Estimates from human rights groups and witnesses range from several hundred to several thousand.

(Reporting by Clare Baldwin; Additional reporting by the HONG KONG newsroom and Ben Blanchard in BEIJING; Editing by Robert Birsel)