China on Wednesday hinted that the military could be deployed in Hong Kong to maintain order and warned pro-democracy protestors it would not tolerate their efforts to threaten the central government’s authority, The New York Times reported.

The warning came as the Chinese defence ministry outlined plans for modernisation of the armed forces. It accused the United States and its allies of undermining global stability and identified separatism as China’s most immediate security threat.

Ministry of Defence spokesperson Wu Qian spoke about the protestors who vandalised the walls of the Beijing representative’s office and defaced the national emblem on Sunday. He suggested that these instances of violence were straining Beijing’s patience. Thousands of protestors had occupied the road outside the representative’s office, and used eggs, projectiles, laser lights and graffiti to deface the building.

“The behaviour of some radical protesters challenges the central government’s authority, touching on the bottom line principle of one country, two systems,” said Colonel Wu . “That absolutely cannot be tolerated.”

Wu also referred to a specific article in the country’s Basic Law that governs relations between the region and Beijing, and allows the People’s Liberation Army to intervene to maintain order or assist in cases of natural disasters when asked by the region’s leaders.

On Monday, China’s top envoy to Hong Kong Wang Zhimin had condemned the demonstrators’ actions.

The protestors are demanding the right to universal suffrage and the resignation of the city’s chief executive Carrie Lam. However, Beijing has not yielded so far. Officials and state-owned media have accused the protestors of playing into the hands of foreign countries seeking to harm China.

The protests had initially been organised to oppose a bill that would have allowed extraditions to mainland China. However, it was suspended earlier this month.