After months of relative restraint, China’s Communist government this week took its most decisive steps to intervene in Hong Kong’s political crisis, signalling a more forceful response that could further inflame tensions in the Chinese territory.

China’s top legislative body, the National People’s Congress, warned that it would use its authority, if necessary, to overrule the territory’s judiciary. It followed a Hong Kong court’s ruling on Monday overturning a contentious ban on wearing face masks, which protesters have used to shield their identities from the police.

The warning struck at the very heart of what has fuelled the unrest, a concern about Beijing’s encroachment on Hong Kong.

The protests began in June over another legal issue: legislation allowing the extradition of criminal defendants into the opaque and notoriously injudicious judicial system of the mainland.

While the bill has since been withdrawn, Beijing has not yielded an inch from its view that the Communist Party remains the ultimate arbiter of justice. That position is especially fraught for Hong Kong, where the court system has been a defining feature of the “one country, two systems” arrangement that promises the territory significant autonomy.

“It represents a new stage in Hong Kong’s protest movement,” Wu Qiang, a political analyst in Beijing, said of the warning from the National People’s Congress, a body that functions as a rubber stamp of the party’s policy agenda. “It has reached the stage of a very direct conflict over sovereignty.”

Although Chinese officials have intensified their denunciations of the protesters as extremists and even blamed the “black hands” of western nations in stoking unrest, they have until now largely left the handling of the crisis to the city’s chief executive, Carrie Lam. Now, Beijing’s patience appears to be wearing out.

Last week, China’s top leader, Xi Jinping, toughened his tone. Xi, who has stirred internal rumblings over the handling of the protests, declared during a visit to Brazil that “the most urgent task” in Hong Kong was “to halt the violence and chaos and to restore order”.

A more aggressive strategy is not without risks for Beijing. The protests have left thousands injured, caused significant material and economic damage, and resulted in the arrest of about 700 people during a siege at one campus this week. It has also rattled international confidence in Hong Kong.

The warning from the National People’s Congress affirmed fears that Beijing is bent on steadily increasing its influence over the territory’s affairs, abandoning its promises to preserve the city’s distinct historical, political and cultural characteristics.