Hong Kong will charge 44 protesters detained during recent violent clashes with rioting, a charge that carries up to 10 years in jail, a senior police source said Tuesday.

"We are in the process of charging them. A formal press statement will be issued later tonight," the source told AFP on condition of anonymity.

Hong Kong has been hit by weeks of mass protest marches — some of which have ended in violence — triggered by a controversial bill which would have allowed extraditions to mainland China.

They have evolved into calls for wider democratic reforms and a halt to sliding freedoms in the most significant challenge to Beijing's rule since the city's 1997 handover.

Recent weeks have seen a dramatic surge in the level of violence used by both protesters and police who have repeatedly fired rubber bullets and tear gas to disperse projectile-throwing crowds.

In the latest clashes on Sunday, protesters fought running battles with riot officers in a well-heeled residential suburb on the main island with 49 arrests made.

Rioting is one of the most serious public order offenses on Hong Kong's statute books and carries a sentence of up to a decade in jail.

Edward Leung, a prominent activist, was jailed for six years last year after he was found guilty of rioting in clashes with police in 2016.

The move to charge the 44 protesters comes a day after Beijing publicly threw its weight behind Hong Kong's unelected leader Carrie Lam and the police, saying violent protesters must be swiftly punished.

"No civilized society or rule of law society will tolerate rampant violence," Yang Guang, spokesman for the cabinet-level Hong Kong and Macau Affairs Office, told reporters in a highly unusual public press conference.

Yang blamed the violence on a "few radicals" and said it "bumped into the bottom line" of the "one country, two systems" principle that governs the financial hub.

He also accused Western politicians of making "irresponsible remarks" to "mess up Hong Kong" and contain China's development.

Beijing has issued increasingly shrill condemnations of the protests, but has left it to the city's government to deal with the situation.

Lam has shown no sign of backing down beyond agreeing to suspend the extradition bill and has made few public appearances.

Protesters have vowed to keep their campaign going until their core demands are met.

They include the resignation of Lam, an independent inquiry into police tactics, an amnesty for those arrested, a permanent withdrawal of the bill and the right to elect their leaders.

On Monday, activists held up trains on the city's subway system during the morning rush hour, leading to lengthy delays and long queues for buses.

It was not the first time they have used those tactics, but the disruption was more widespread than previously.

Under the 1997 handover deal with Britain, China promised to allow Hong Kong to keep key liberties such as its independent judiciary and freedom of speech.

But many say those provisions are already being curtailed, citing the disappearance into mainland custody of dissident booksellers, the disqualification of prominent politicians and the jailing of pro-democracy protest leaders.