Weeks of increasingly violent protests have plunged Hong Kong into its most serious political crisis for decades, posing a serious challenge to the central government in Beijing.

On Saturday activists rallied across the city - with thousands thronging the airport arrivals hall for a second day - while elsewhere police displayed a new willingness to quickly and forcibly clear them from the streets.

Tear gas was used with little warning not long after several hundred activists who had marched through Tai Po in the north of the territory had barricaded an intersection in the Tai Wai neighborhood.

They dispersed, as noxious smoke also filled the underground station there, bringing train passengers to tears.

“If the government thinks we’ll give up and not come out anymore they’re wrong,” said student Chris Wong, 20, at Tai Po.

“Carrie Lam is now spreading lies and blaming us for destroying Hong Kong’s economy. But she’s the one who is destroying Hong Kong,” he said. “We’ll continue to fight...but we’re also going to be smart and wear them down.”

Lam, Hong Kong’s leader, said on Friday the economy was being undermined by the protests, which began in June.

China, meanwhile, demanded that the city’s flag carrier Cathay Pacific Airways (0293.HK) suspend staff involved in the demonstrations. One of its pilots was arrested last week.

Lam’s warning about the economy and China’s targeting of a key Hong Kong business mark a toughening stance by authorities as they grapple with the crisis.