China told Britain to keep its hands off Hong Kong while London called for Beijing to honour the agreements made when the city was handed over in 1997, escalating a diplomatic spat over the former British colony.

Beijing denounced British Foreign Secretary Jeremy Hunt as “shameless” and said it had made a diplomatic complaint to London after he warned of consequences if China neglected its commitments to guarantee basic freedoms.

“In the minds of some people, they regard Hong Kong as still under British rule. They forget … that Hong Kong has now returned to the embrace of the Motherland,” China’s ambassador to London, Liu Xiaoming, said on Wednesday.

“I tell them: hands off Hong Kong and show respect. This colonial mindset is still haunting the minds of some officials or politicians,” Liu told reporters.

The growing war of words between China and Britain follows mass protests in Hong Kong against a now suspended bill that would allow extradition to mainland China.

Hundreds of protesters in the former British colony besieged and broke into the legislature on Monday after a demonstration marking the anniversary of return to Chinese rule.

China called the violence an “undisguised challenge” to the “one country, two systems” model under which Hong Kong has been ruled for 22 years.

On Tuesday, Hunt warned of consequences if China did not abide by the Sino-British Joint Declaration in 1984 on the terms of the return of Hong Kong, which allows freedoms not enjoyed in mainland China, including the right to protest.

“We can make it clear we stand behind the people of Hong Kong in defence of the freedoms that we negotiated for them when we agreed to the handover in 1997 and we can remind everyone that we expect all countries to honour their international obligations,” Hunt told Reuters.

Hunt is one of two contenders vying to replace Theresa May as British prime minister and his rival Boris Johnson told Reuters on Wednesday that he also backed the people of Hong Kong “every inch of the way”.

The comments clearly irked Beijing. China’s London envoy scolded Britain and said meddling in Hong Kong would cause a “problem in the relationship” between them.

“The UK government chose to stand on the wrong side: it has made inappropriate remarks not only to interfere in internal affairs of Hong Kong but also to back up the violent law-breakers,” Liu said.

Earlier, Foreign Ministry spokesman Geng Shuang chided Hunt, saying that only after Hong Kong’s return to China did its people get an “unprecedented” guarantee about democracy and freedom.

“To say that the freedoms of Hong Kong residents is something Britain strived for is simply shameless,” he told a news briefing.

Feelings are running high in Hong Kong.

“I would like to ask Mr. Hunt, during the British colonial era in Hong Kong, was there any democracy to speak of? Hong Kongers didn’t even have the right to protest.”

China had lodged “stern representations” with Britain both in Beijing and London about Hunt’s remarks, he added.

Britain said it had summoned Liu to the foreign office following his “unacceptable” comments, a government source said.

“Message to Chinese govt: good relations between countries are based on mutual respect and honouring the legally binding agreements between them,” Hunt said on Twitter after Liu’s media briefing.

“That is the best way to preserve the great relationship between the UK and China.”

Hong Kong police have arrested 12 people in connection with the recent tumult although it was unclear if they were among protesters who smashed their way into the city’s legislature and ransacked the building.

The police say they have also arrested six people linked to incidents the day before, and eight others suspected of being involved in the illegal disclosure online of police officers’ private information.

-AAP