"Every time I walk home I can't get through because I'm blocked by a horde of [mainlanders] with luggage on the pavement," said one Tuen Mun resident called Chris.

One of the march leaders was Civic Passion's Cheng Chung-tai, who called the buses "private coaches for parallel traders". He urged protesters to help Citybus staff clamp down on the practice. "Tuen Mun residents, counting on the authorities ... will no longer work. You must take charge of your own district," he said.

The jeering and taunting were met with mixed responses from parallel-goods traders. Some took photos of the protest, while a few raised their middle finger at the protesters as their buses left.

From the bus stop, protesters marched to Yan Ching Street, an area full of pharmacies and gold shops, where they demonstrated against the impact of parallel trading. Some shops closed.

The protesters then moved to nearby malls to mount Mong Kok-style , or shopping, protests.

One scuffle between a couple and a group of protesters in Tuen Mun Town Plaza turned into a shoving match, which prompted officers to use pepper spray.

Batons were drawn and a red warning flag was raised.

By nightfall, shops at nearby Trend Plaza were forced to shut as protesters took over nearly half of the mall. Police used batons and pepper spray as they clashed with protesters. Injuries were sustained on both sides - including a police officer, who briefly fell unconscious. Thirteen locals - nine men and four women, aged 16 to 74 - were arrested.

"Yes it was chaotic, but I think it was very successful as we really got our message out to the parallel traders," said Andy Yung Wai-yib, holding a colonial-era flag. He was better known as "Captain America" during the 79-day Occupy sit-ins.

The police issued a statement last night urging the public to be rational in expressing their views.