Police fire teargas in Hong Kong's biggest lockdown-era protests

Black-clad protesters and tear gas returned to Hong Kong's streets on Sunday (May 24).

But if you're suffering from a sense of deja vu - here's what's new: these are the biggest protests since lockdown restrictions began.

The reason: Beijing's plan to impose national security laws on the city.

Thousands marched through Causeway Bay amid fears that the 'one country, two systems' formula - which guarantees broader freedoms for the global financial hub than exist on the mainland, is under threat from China's tightening grip.

Democratic Party politician Lam Cheuk-Ting said the situation is critical:

"We are worried that the Chinese Communist Party is using the evil law to further suppress Hong Kong people."

Sunday's rally was initially organised against a controversial national anthem bill, but the proposed national security laws sparked calls for more people to take to the streets.

Police fired teargas to disperse crowds in chaotic scenes reminiscent of last year's at times violent mass protests and some protesters tried to set up roadblocks.

China has dismissed an international outcry over the proposed legislation as "meddling" and says the laws are "necessary" and will not harm Hong Kong's autonomy or foreign investors.

But the backlash against Beijing's play intensified on Saturday (May 23) as 200 political figures from around the world said in a statement that the proposed laws are a quote: "comprehensive assault on the city's autonomy, rule of law and fundamental freedoms."