An elderly Catholic missionary in Hong Kong has launched a three-day hunger strike outside a high-security prison demanding the release of politicians and activists incarcerated under the city's Beijing-imposed controversial national security law.

Father Franco Mella, 74, a member of the Milan-based Pontifical Institute of Foreign Missions, has vowed to abstain from food as he started his protest near the Shek Pik prison on Lantau Island in Hong Kong July 14 amid sweltering summer heat, Reuters reported.

"The weather is so hot. So, they are suffering inside. And the message (is) we are with you, do not lose hope. Let us continue to fight for everybody's freedom," Father Mella said.

With temperatures in the mid- to upper 80s Fahrenheit, the task of abstaining from food has become even more challenging for the priest.

The Milan-born priest arrived in Hong Kong in 1974, and since then has advanced human rights and freedom for the people of the Chinese-ruled city-state.

A Hong Kong government spokesperson, however, said the arrests were lawful and based on evidence. "It would be contrary to the rule of law to suggest that people of certain backgrounds could be above the law," the spokesperson said.

About 200 people, including activists and politicians, have been arrested and charged under the national security law imposed by China in June 2020 to suppress a series of pro-democracy protests that erupted in 2019.

A top U.S. diplomat in Hong Kong, Hanscom Smith, who ended his three-year term July 11, warned Beijing that it cannot expect Hong Kong to maintain its long-standing role as a global financial and business center if it continues the "crude and chilling" use of the repressive law.

Meanwhile, the U.N. Human Rights Committee began reviewing Hong Kong's rights record July 7 for the first time since Beijing imposed the national security law.

Father Mella was also among the Christian representatives who handed over a letter to then-Hong Kong Chief Executive Carrie Lam, pleading for the release of Jimmy Lai and other activists in February.

Lai, a Catholic entrepreneur and media tycoon, founded the now-defunct popular newspaper Apple Daily in 1995. The Chinese government forced the newspaper to shut down in June 2021 because of its staunch pro-democracy reporting.

Father Mella staged a similar "silent protest" in January at Lai Chi Kok Reception Center, where 47 pro-democracy activists were detained for more than 300 days.

The national security law has triggered international condemnation as it has become the most repressive tool to muzzle dissent in Hong Kong, a former British colony.

The law effectively has diminished freedoms, rights and a higher degree of autonomy, including an independent judiciary and legislature, guaranteed in the "one country, two systems" framework in the Sino-British Joint Declaration of 1984. The declaration established the conditions in which Hong Kong was transferred to Chinese control and for the governance of the territory beginning July 1, 1997.

The erosion of freedoms in Hong Kong started in 2019, when Lam proposed a controversial extradition bill, which sought to allow Hong Kong suspects to be sent for trial in China. The bill triggered massive public protests as anti-China and pro-democracy movements nearly crippled the city.

The bill was later withdrawn. Instead, the communist regime imposed the national security law to suppress pro-democracy politicians and supporters.

The arrests under the law, including those of Catholic politicians and activists, sparked global outrage.

In May, Hong Kong police arrested 90-year-old Cardinal Joseph Zen Ze-kiun, a former bishop of Hong Kong diocese along with other activists on a charge of "colluding with foreign forces" for allegedly supporting pro-democracy protesters.

Following a global outrage, Cardinal Zen was released shortly after.