Hong Kong police on Saturday fired tear gas and rubber bullets to disperse hardcore protesters who built barricades in a mainly working-class satellite town in the northwest of the territory.

Police warned the activists in Tuen Mun in the New Territories to scatter before deploying the chemical and rubber-coated projectiles. Tensions spiked when some protesters threw bricks and Molotov cocktails at officers. Several people were arrested.

Thousands of people took part in an earlier, peaceful rally from the town's park to government offices, where some protesters set fire to a Chinese flag.

Read more: Joshua Wong: Hong Kong protests 'must continue'

The turnout was much smaller than in previous weeks, and protesters were mostly dressed in black, carried umbrellas and chanted: "Reclaim Hong Kong!" and "Revolution of our times!"

Rail stations in the nearby town of Yuen Long were shut ahead of a sit-in on Saturday evening to mark two months since an attack on protesters by triad gangs operating in Hong Kong and South China.

After the sit-in, skirmishes broke out between protesters and police, who were accused of having been too slow to respond to the triad attack.

Post-it note campaign destroyed

Earlier, dozens of Beijing supporters tore down some of the colorful message boards put up by protesters all over the Asian financial center, calling for electoral reforms in the semi-autonomous Chinese territory.

A pro-Beijing city legislator, Junius Ho, who has been a vocal critic of the protests, had urged his supporters to clean up approximately 100 so-called Lennon walls of Post-it notes around the city, leading to scuffles with protesters.

Read more: Hong Kong crisis — What you need to know

Now in its fourth month, Hong Kong's protest has morphed from anger over a plan to allow extradition to the mainland — which has now been withdrawn — to a long list of grievances against the territory's government led by Chief Executive Carrie Lam.

Beijing and London negotiated a "high degree of autonomy" for Hong Kong when the former British colony was returned to China in 1997. But protesters complain that Beijing is increasingly undermining the "one country, two systems" principle.

Weeks of massive, sometimes violent protests show no sign of ending, despite the city's leaders and Beijing taking a hard line.

Amnesty backs criticism of police

Protesters say they want full universal suffrage, as only half of Hong Kong's 70-member Legislative Council is picked by the public. Activists have also demanded an independent inquiry into alleged police brutality during the protests, which on Friday was backed by Amnesty International.

Read more: Hong Kong protesters' personal data leaked by Russian website

In a report based on interviews with nearly two dozen activists, the human rights group accused Hong Kong police of using excessive force against demonstrators.

Amnesty said officers routinely went beyond the level of force allowed by local law and international standards, which in some cases amounted to torture.

Videos of police baton-charging and beating protesters have frequently gone viral online during clashes that saw protesters hurl rocks, bottles and petrol bombs at officers.

The Hong Kong police force dismissed Amnesty's findings and said in a statement that their officers "exercise a high level of restraint at all times."

mm/sms (AFP, AP, dpa, Reuters)

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