Flashmob rallies erupted inside multiple shopping centers across the international finance hub over the afternoon, sparking frequent clashes with riot police.
The violence was less sustained than Saturday when police and protesters fought hours of cat and mouse battles after thousands took the streets for an unsanctioned march.
But the day ended with a knife attack taking place outside a shopping mall in Tai Koo Shing, a middle-class neighbourhood on the main island where protesters had gathered for much of the afternoon.
Eye-witnesses told local media that a Mandarin-speaking man attacked people shortly after shouting pro-Beijing slogans.
Live footage showed Andrew Chiu, a local pro-democracy councillor, having his ear bitten off after trying to subdue the attacker, while a second man was seen unconscious in a growing pool of blood as bystanders desperately tried to stem wounds to his back.
The alleged assailant, wearing a grey t-shirt, was then beaten bloody by the crowd until police and other emergency workers arrived.
Hospital authorities said five people were wounded, four men and one woman.
Two victims were in a critical condition, two were serious and one was stable.
Police revised down their wounded toll from six to five people and said three people were arrested, without detailing whether the alleged knife attacker was among those counted as injured or arrested.
An eye-witness, who gave her surname Leung, told RTHK News that the man shouted in Mandarin -- the language spoken on the Chinese mainland -- before attacking her brother-in-law who argued with him.
"The man came out from the doorway and yelled a sentence in Mandarin, it seemed like liberate Taiwan or something," she said.
Speaking to reporters outside the hospital where Chiu was taken to, pro-democracy lawmaker James To said the attacker shouted "reclaim Taiwan and Hong Kong".
Communist China views self-ruled Taiwan as its own territory and has vowed to one day seize it, by force if necessary.
Hong Kong has been upended by the huge, often violent, pro-democracy protests which have battered the financial hub's reputation for stability and helped plunge the city into recession.
Police are firing ever increasing rounds of tear gas and rubber bullets against small groups of hardcore protesters who have embraced throwing petrol bombs as well as vandalising pro-China businesses.
With the city desperately polarised, street fights have broken out on both sides of the ideological divide with growing frequency.
Beijing supporters have attacked opponents throughout the summer, often in targeted assaults against prominent government critics and opposition politicians.
Earlier this month a man handing out pro-democracy flyers was stabbed in the stomach by a man who shouted slogans in Mandarin and was later arrested.
In Hong Kong, the lingua franca is Cantonese.
But the violence is far from one-sided.
Crowds of pro-democracy protesters have also routinely beaten their ideological opponents, usually in spontaneous mob violence during rallies.
With no political solution in sight, there are few signs of the spiralling violence and polarisation letting up.
Beijing has shown no willingness to meet demonstrators demands for greater democratic freedoms and police accountability -- and activists show no sign of leaving the streets with 22 consecutive weekends of unrest.
This summer's first protests in which millions marched were sparked by a now-abandoned attempt to allow extraditions to the mainland.
But as Beijing took a hardline the movement snowballed.
Protesters are demanding an inquiry into the police, an amnesty for those arrested and fully free elections. (AFP)