It’s unclear whether the actions were an expression of frustration or backed by pro-Beijing factions.

HONG KONG — Opponents of a week-long protest in Hong Kong stormed into demonstrators’ midst Friday, attacking them and pulling down their tents and barricades.

The violence injected fresh fear among student protesters as well as anger and suspicion at authorities’ delayed and tepid response and their seeming reluctance to arrest anti-protest attackers.

The rapidly deepening mistrust could make confrontation between authorities and protesters more likely. And the clash reflects growing polarization throughout Hong Kong over the protesters’ occupation downtown, which has paralyzed major sections of the city.

Some protesters openly accused police of colluding with the attackers Friday, and organizers threatened to call off planned talks with the government.

It was unclear whether the simultaneous attacks at two separate camps Friday were a spontaneous expression of residents’ frustration with how the protest has paralyzed large swaths of the city, or whether they were sanctioned by pro-Beijing factions.

But fueling protesters’ suspicions, some attackers were heard speaking with mainland accents, and according to witnesses, at least one was carrying a sign written in simplified characters used on the mainland but not in Hong Kong.

Protesters accused the counter-demonstrators of being thugs sent by Hong Kong’s triads and mainland Chinese authorities, who have opposed the protests and warned that their continuation would send Hong Kong into “chaos.”

“First they told us there would be chaos, and now they have made it happen,” said one demonstrator at one of the attacked sites, who was only willing to give his last name, Fai, for fear of inviting attacks against him.

“The failure of police to stop or punish the violence is certainly feeding into perceptions that what happened is some sort of collusion,” said Maya Wang of the Human Rights Watch. The suspicions further undermined an already fragile situation.

In the working-class neighborhood Mong Kok, which has long been associated with triad gangs, student protesters were hemmed in on all sides by counter-protesters, who were kept back only by a thin cordon of wildly outnumbered police.

The Hong Kong Federation of Students, one of the main protest groups, said the “government and police have allowed triad members to violently attack peaceful occupiers.”