British Foreign Secretary Jeremy Hunt and Prime Minister Theresa May pledged their support for Hong Kong protesters on Tuesday, a day after anti-government rallies marked the anniversary of the city's return to China.

Hunt called on Hong Kong's pro-Beijing authorities not to use the protests as a "pretext for repression."

"We are very concerned about the violence we have seen on all sides during the protests," he added.

Hunt, who is also running to succeed Theresa May as prime minister, also said Beijing must honor the 1997 treaty that saw Britain return Hong Kong to China.

"There will be serious consequences if that internationally binding legal agreement were not to be honored," he said.

The treaty included an agreement on a "one country, two systems" principle, which protects Hong Kong's freedoms and judicial independence.

May's spokesman said China should "address the deep-seated concern by the people of Hong Kong that their basic freedoms are under attack."

'Purely an internal matter'

Chinese representatives had previously demanded that Britain stop "gesticulating" about Hong Kong's affairs.

"Hong Kong matters are purely an internal affair for China," Chinese Foreign Ministry spokesman Geng Shuang told reporters on Monday. "We urge Britain to know its place and stop interfering in any form in Hong Kong matters and do more for its prosperity and stability rather than the opposite."

On Tuesday, China's foreign Ministry released a statement voicing its "strong dissatisfaction and resolute opposition" to pro-protester statements by Britain, the United States and the European Union.

The ministry said other countries should "immediately stop their wrong words and deeds" to interfere in the internal affairs of the city.

Storming the legislature

During protests on Monday, Hong Kong police fired tear gas to disperse protesters and went into the crowds armed with batons. A number of protesters stormed the Hong Kong legislature, daubing graffiti on the walls and trashing rooms.

The clashes came after weeks of massive rallies against a proposed law that would allow Hong Kong residents to be extradited to China for court hearings.

Pro-democracy activists fear that city residents would face an unfair legal system as a result. They also see the move as the latest example of growing Chinese encroachment on Hong Kong's internal affairs.

Read more: China 'won't allow' Hong Kong discussion at G20 summit

The side of the Hong Kong parliament was badly damaged

Carrie Lam, the city's pro-Chinese chief executive, has urged the protests to stop. She suspended the extradition bill last month but did not scrap it, a key demand from the protesters.

Demonstration organizers have vowed to continue until the bill is dropped.

Every evening at 1830 UTC, DW's editors send out a selection of the day's hard news and quality feature journalism. You can sign up to receive it directly here.

jns/amp (Reuters, AP)