China suspended Hong Kong's extradition treaty with New Zealand on Monday amid a row with Western nations protesting against a tough new security law that Beijing imposed on the city.

New Zealand is the latest to join a string of Western powers -- including Canada, Britain, Australia and Germany -- that have suspended extradition treaties with Hong Kong since the controversial law was introduced in late June.

China has already hit back by suspending Hong Kong's extradition treaties with Canada, Britain and Australia. "New Zealand's practices... grossly interfere in China's internal affairs," foreign ministry spokesman Wang Wenbin said, announcing Beijing's decision to suspend any judicial cooperation with Wellington.

Critics say the security law will erode civil liberties and human rights enjoyed by residents in the former British colony, which was returned to China in 1997. New Zealand has also tightened restrictions on military and dual-use exports to Hong Kong.

Its latest travel advice to Kiwi citizens in the territory said the security law had led to an increased risk of arrest for activities such as protests, with the possibility of being removed to mainland China to face a maximum penalty of life imprisonment.

The United States has decided to rescind Hong Kong's special trading privileges after the new law was enacted.