Screams rang out when men, clad in white t-shirts and some armed with poles, flooded into the rural Yuen Long station and stormed a train, attacking passengers, according to footage taken by commuters and Democratic Party lawmaker Lam Cheuk-ting.

Some passengers had been at an earlier anti-government march and the attack came after several thousand activists surrounded China’s representative office in the city, later clashing with police.

Lam, who was injured in the attack, said he was angry about a slow police response after he alerted them to the trouble, government-funded broadcaster RTHK reported.

Lam said the police action had failed to protect the public, allowing the triads to run rampant. The party is now investigating.

“Is Hong Kong now allowing triads to do what they want, beating up people on the street with weapons?,” he asked reporters.

Hong Kong has been rocked by a series of sometimes violent protests for more than two months in its most serious crisis since Britain handed the freewheeling city back to Chinese rule in 1997.

Protesters are demanding the full withdrawal of a bill to allow people to be extradited to mainland China for trial, where the courts are controlled by the Communist Party, and independent inquiries into the use of police force against protesters.

On Sunday police fired rubber bullets and tear gas to disperse crowds of activists on the edge of Hong Kong’s glittering financial district after they had fled China’s Liaison Office.

The Chinese government has condemned the action, which saw signs and a state symbol daubed with graffiti.

The continuing unrest in Hong Kong marks the greatest popular challenge to Chinese leader Xi Jinping since he came to power in 2012.

The Hospital Authority said 45 people were injured in the Yuen Long attack, with one in a critical condition. Some 13 people were injured after the clashes in Hong Kong island, one seriously, the authority said.

In a statement early on Monday, police “strongly condemned” both violent incidents and were investigating both cases.

Some police had been injured in the clashes after protesters hurled bricks, smoke grenades and petrol bombs, the statement said. (Reporting by Donny Kwok, Vimvam Tong and Greg Torode.)