HONG KONG (BLOOMBERG) - Some of Hong Kong's pro-democracy politicians have begun offloading long-held properties as China steps up its control over the city.

Lee Cheuk-yan, Lam Cheuk-ting, Au Nok-hin and Audrey Eu have each sold an apartment recently, according to documents lodged with the Land Registry.

"I have five criminal cases against me and the legal fees will be very costly," said Lam, a former lawmaker who sold his apartment in the Sha Tin area for HK$12.7 million (S$2.2 million) last month. "The legal costs are a heavy burden, and I also want to let my children study overseas. So it was my decision to sell the apartment to help prepare for all the expenditure."

Lee, a veteran political activist, says he's cashing in because he expects property prices to fall as Hong Kongers take advantage of a new pathway to citizenship in the UK and leave the city. He sold an apartment in Kowloon for about HK$10 million in January to fund his retirement.

"I wanted to sell at a good price," said Lee. "With the trend of emigration in the city, those in their 40s and 50s are most likely to leave and sell their properties. So I expect home supply to go up while demand declines." Lam and Lee said they will now rent.

Au and Eu declined to comment.

The pro-democracy politicians' move to offload property is common among residents plotting their exit due to Hong Kong's dwindling freedoms after China implemented a controversial national security law, which prohibits subversion, terrorism, secession and "collusion" with foreign forces.

While China has said the law is necessary to restore stability after the protests in 2019, foreign governments said the legislation has been used to target democracy activists and is eroding freedoms Beijing pledged to maintain after the 1997 handover.

The UK estimates about 300,000 Hong Kong residents, or 4 per cent of the city's total population, may make use of the new visa route to emigrate.

Property agencies have seen a surge in listings. The number of properties for sale at Centaline Property Agency, Hong Kong's largest realtor, jumped 44 per cent from a year ago to more than 38,000 in February.

The potential outflow of people would also harm Hong Kong's rental market. Rents could fall by 6 per cent in 2021 as some families move to the UK, said Patrick Wong, an analyst with Bloomberg Intelligence.

Lee, Au and Lam have been charged with offences including rioting and illegal assembly for their involvement in anti-government protests in 2019.