Beijing warned Washington Monday of retaliation after President Donald Trump announced restrictions on Chinese students in the US in protest over a new national security law in Hong Kong.

Trump said Friday that the United States would ban some Chinese graduate students and start reversing Hong Kong’s special status in customs and other areas, as Beijing moves ahead with a plan to impose a controversial security law.

The US president said the Chinese government had been “diminishing the city’s longstanding and very proud status”.

But China reacted angrily to the moves on Monday, saying it was “detrimental to both sides”.

“Any words and actions that harm the interests of China will be met with counter-attacks on the Chinese side,” said foreign ministry spokesman Zhao Lijian at a regular briefing, without providing details.

He said Washington’s measures “seriously interfere in China’s internal affairs and undermine US-China relations”.

China’s rubber-stamp parliament on Thursday approved plans for the law, which would punish secession, subversion of state power, terrorism and acts that endanger national security, as well as allow Chinese security agencies to operate openly in Hong Kong.

The move followed seven months of huge and sometimes violent pro-democracy protests in Hong Kong last year.