New Zealand and Australia have issued a joint statement, expressing deep concerns about changes to Hong Kong's electoral system.

Issued by Foreign Affairs Minister Nanaia Mahuta and her Australian counterpart senator Marise Payne, it said thechanges passed by China further undermine rights and freedoms and the high degree of autonomy guaranteed to Hong Kong until 2047, under the Sino-British Joint Declaration.

And that Hong Kong, as a significant finance and trade hub, must continue to enjoy a high degree of autonomy to succeed.

The resolution to overhaul Hong Kong's electoral system was approved by the Chinese legislature this week, and will allow a pro-Beijing panel to vet election candidates. It could be in place within months.

China's President Xi Jinping (centre) applauds with other leaders after the result of the vote on changes to Hong Kong's election system was announced in a session of the National People's Congress on Thursday. Photo: AFP

Mahuta told RNZ that Australia and New Zealand are calling for the promised 'one country, two systems' constitutional principles to be upheld.

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"Just last week we heard that charges have been laid against 47-odd opposition representatives, signalling a continued erosion of democratic freedom, but also escalating concerns from the international community about the impact on those in Hong Kong."

"These changes run contrary to the ultimate aim of a Hong Kong Chief Executive elected through universal suffrage, weaken Hong Kong's democratic institutions, and erode freedom of speech and association - all of which are set out in the Basic Law," the statement from Mahuta and Payne said.

The two urged Hong Kong and Chinese authorities to uphold their commitments to allow Hong Kong's people genuine participation in their governance, and to be allowed to scrutinise the government and express diverse views.

Hong Kong's Legislature Photo: AFP

What about international reaction?

UK Foreign Secretary Dominic Raab said the dilution of elections in Hong Kong would further undermine trust in China.

However, the Chinese embassy in London's chargé d'affaires Yang Xiaoguang told the BBC that the UK and China had a "different definition" of democracy.

Asked about possible UK sanctions against Chinese individuals over Hong Kong and other issues, Yang said China would "safeguard our interests at any cost".

Earlier, the US condemned China's "continuing assault on democratic institutions in Hong Kong".

A busy shopping street in Hong Kong's Causeway Bay district. Photo: 123rf

What has the reaction in Hong Kong been?

"What they're really referring to [when they say 'patriot'] is that they will pick the people that they like, someone who is one of them," one resident told BBC Chinese.

"Basically, it's a step backwards, becoming more and more like the mainland," he said.

But another resident, identified as Ho, said she supported the law.

"Hong Kong has already returned [to China]." She said. "So under this situation, the Chinese government's law should be the framework for our [patriot law]."