A general who led China's anti-terrorism special forces in Xinjiang has been promoted to head up the People's Liberation Army in Hong Kong, state media has reported.

The appointment comes as Beijing is remoulding the international business hub in its own authoritarian image after huge and sometimes violent democracy protests in 2019.

Under the city's mini-constitution, Hong Kong has its own police force but China has maintained military barracks there since the city's 1997 handover when colonial Britain's forces left.

A new national security law has also empowered the mainland's security agents to operate openly in the city.

China's official Xinhua news agency announced on Sunday that major general Peng Jingtang, deputy chief of staff of the People's Armed Police, has been appointed the Hong Kong garrison's commander by president Xi Jinping.

Among the few details released on state media about Peng's career is his former post as the chief of staff of the Armed Police Corps in Xinjiang, part of China's paramilitary police force.

Three years ago Reference News -- a branch of Xinhua -- reported that a new special force called Mountain Eagle Commando had been formed in Xinjiang "for the anti-terrorism needs in the region and across China".

Peng was quoted in the report as being the force's leader.

"Every single bullet of ours is aiming at the battlefield," he was quoted as saying, alongside revealing that the ammunition spent by Mountain Eagle in training sessions over a single year was three times what other units use.

China has blanketed western Xinjiang in a security crackdown in recent years after ethnic riots in the capital followed by attacks by Uyghur militants.

Dense deployment of paramilitary forces and massive surveillance systems were installed to stamp out what the ruling Communist Party described as widespread Islamic extremism and separatism in the region.

Campaigners say at least one million Uyghurs and other Turkic-speaking, mostly Muslim minorities have been detained in Xinjiang camps alongside a deliberate campaign to assimilate the minority group's religion, language and culture.

Washington has labelled the crackdown a genocide.

After initially denying the existence of the Xinjiang camps, China later defended them as vocational training centres aimed at reducing the appeal of Islamic extremism and Beijing denies a genocide is taking place.

Peng is replacing his predecessor Chen Daoxiang, who is reaching the retirement age.

Under Chen's leadership, Hong Kong's PLA soldiers have become more visible -- during the 2019 protests they cleared debris following a clash between demonstrators and police, as well as holding frequent drills simulating crowd control and anti-terrorism operations.

China's leadership has dismissed the city's huge democracy rallies, portraying the movement as "local terrorism" and separatism, rhetoric similar to that used for Xinjiang.

Dozens of prominent democracy campaigners are in jail on national security charges.