Hong Kong riot police spent much of Sunday afternoon skirmishing with groups of masked pro-democracy protesters who held flashmob gatherings in multiple locations - although crowds were smaller and less violent than recent weekends.

Rallies erupted in multiple neighbourhoods with some protesters blocking roads, throwing objects onto train tracks as well as spraying graffiti and smashing the windows of some pro-China businesses.

Police made dozens of arrests as they rushed to intercept activists but the clashes were less sustained than earlier in October when the city was virtually shut down by the most intense unrest of the four month protest movement.

In the district of Mongkok, riot police burst from an unmarked van that had screeched up to a blockade made of bamboo scaffolding poles and quickly chased down multiple protesters who were pinned to the ground and detained.

Later an AFP reporter in the same neighbourhood saw crowds of protesters beat a middle aged woman because she had helped police clear barricades.

The woman was struck with fists and umbrellas and also had her face smeared with mud.

Protester mobs have increasingly turned on their ideological opponents in recent weeks - while Beijing loyalists have attacked democracy activists throughout the summer.

In Tai Po district, officers charged into a mall where protesters had tagged a number of businesses with slogans. A nearby government office had also been vandalised.

Police said tear gas was fired in two districts while flashmobs and brief clashes were witnessed in at least four other locations.

In online forums used to organise the largely leaderless movement, protesters had given Sunday's rally the theme "blossom everywhere" encouraging activists to gather in malls across the city.

While the crowds were smaller, the cat and mouse tactics stretched police resources thin and were still able to bring chaos to parts of the city in what was a 19th consecutive weekend of protest.

Throughout the day, police found themselves berated and heckled by bystanders as they made arrests, highlighting how the force has become loathed among large parts of the population.

"I'm furious," a female protester, who gave her surname Chan, told AFP. "I want the government to disband the entire police force."

Months of protest

Hong Kong has been shaken by four months of massive democracy protests which have seen increasingly violent clashes between hardcore demonstrators and police, as well as regular transport disruptions.

The wave of protests in the international finance hub was sparked by opposition to a now-scrapped proposal to allow extraditions to mainland China, but has since morphed into a larger movement for democracy and police accountability.

The city enjoys unique rights under the terms of its handover to China by Britain in 1997, including freedom of expression and an independent judiciary, but many believe these are under threat from an increasingly assertive Beijing.

Street battles between riot police and small groups of protesters have become a weekly occurrence, hammering the already struggling economy, spooking tourists and undermining Hong Kong's reputation for stability.

The beginning of October saw a particularly fierce period of unrest with protesters upping their violence as Communist China celebrated its 70th birthday party.

Clashes further intensified after the city's leader invoked colonial-era emergency laws to ban face masks at protests.

Over the course of a week, protesters went on a vandalism spree, much of it targeting the city's subway network and pro-China businesses.

Police also increased their response, firing tear gas and rubber bullets with renewed ferocity. Two teenagers were wounded with live rounds during clashes with police.

But the last few days have seen a comparatively calmer period.

Protesters are pushing for an independent inquiry into the police, an amnesty for the more than 2,500 people arrested and universal suffrage.

Beijing and city leader Carrie Lam have repeatedly rejected those demands.