Hong Kong police said they had arrested 26 in confrontations with a crowd that had swelled to 9000. Fifteen officers were injured.
It was the third consecutive night of violence after a fortnight of comparative calm.
Protesters are calling for free elections and the resignation of the city's leader Leung Chun-ying.
They have held sit-ins at three major intersections, causing significant disruption and presenting China with one of its biggest political challenges since the 1989 Tiananmen Square demonstrations.
Earlier, police carried out a dawn raid on the northern Mongkok camp that saw no resistance from demonstrators. Violence broke out after several protesters tried to push through a police cordon and officers in riot gear responded with baton strikes and pepper spray.
"We've come here peacefully, to peacefully protest for our future," said protester Peter Yuen.
On Thursday the government announced it had resumed talks with the Hong Kong Federation of Students, one of the groups leading the protests, after abruptly pulling out of discussions a week earlier.
But questions were soon raised over whether the talks could achieve a substantive breakthrough.
The government was unwilling to cede to protesters' core demands and Leung adamant that police would continue to clear demonstrator-held barricades.
AAP
