The European Parliament on Friday condemned China's new national security law for Hong Kong as a "comprehensive assault" on the territory's freedom and demanded the EU prepare sanctions.

In a resolution passed just days before a major EU-China summit, MEPs warned Beijing against eroding the special freedoms and autonomy Hong Kong has enjoyed since being handed over to China by Britain in 1997.

"The unilateral introduction of national security legislation by Beijing in Hong Kong... is a comprehensive assault on the city’s autonomy, rule of law, and fundamental freedoms," the parliament said.

The resolution backed EU foreign policy chief Josep Borrell's call for a more "robust" approach to dealing with China, which has grown ever more assertive under President Xi Jinping.

And it urged EU Council chief Charles Michel and European Commission President Ursula von der Leyen to make Hong Kong and human rights a top priority in the agenda for Monday's video summit.

The resolution, which is not binding, urged EU member states to adopt "sanctions and asset freezes against Chinese officials responsible for devising and implementing policies that violate human rights".

The parliament "strongly condemns the constant and increasing interference by China in Hong Kong's internal affairs", according to the resolution.

The Group of Seven foreign ministers on Wednesday urged China to reconsider the proposed security law for Hong Kong, saying they had "grave concerns" it threatens the city's rights and freedoms.

Under a "One Country, Two Systems' deal ahead of the handover by Britain, China agreed to let Hong Kong maintain certain liberties and autonomy until 2047 -- including legislative and judicial independence.

Beijing says the new national security law is needed to end political unrest and restore stability, after a year of huge and often violent rallies for democracy.