At the same time a Chinese official in Beijing warned signs of “terrorism” were emerging. China’s People’s Armed Police also assembled in the neighboring city of Shenzhen for exercises, the state-backed Global Times newspaper said.

Both moves lift the stakes sharply after a weekend of skirmishes between police and activists, in which both sides appeared to boost their resolve with new tactics.

Some of the 5,000 activists occupying the airport’s arrivals hall for a fourth day went to the departure area and caused disruptions, Hong Kong police told a news conference, but declined to say if they would move to clear the demonstrators.

Traffic to and from the airport was severely affected.

“Airport operations at Hong Kong International Airport have been seriously disrupted ... all flights have been canceled,” the city’s airport authority said in a statement.

“All passengers are advised to leave the terminal buildings as soon as possible.”

Roads to the airport were congested and car parks were full, the authority said.

The increasingly violent protests have plunged the Chinese-ruled territory into its most serious crisis in decades, presenting Chinese leader Xi Jinping with one of his biggest popular challenges since he came to power in 2012.

Monday’s cancellation came as China’s Hong Kong and Macau Affairs office said the city had reached a critical juncture and after police had made a show of demonstrating a powerful water cannon.

REUTERS