Twenty Hong Kong protesters were reportedly injured early Sunday as a result of what they say is continued police brutality.
The violence comes ahead of meetings between protest leaders and Hong Kong government officials on Tuesday.
Demands for free elections in 2017 have sparked thousands of protesters to occupy main business areas over the past several weeks.
Reuters reports on the police response Sunday to the protesters moving barricades that had blocked them in:
Amid screams and cursing, hundreds of officers began whacking the protesters who raised a wall of umbrellas. Pepper spray was used intermittently amid violent scuffles. The police then surged forward with riot shields, forcing protesters back.
"We believe police have violated the principle of using minimum force to deal with peaceful demonstration," Agence France-Presse quotes James Hon of protest group The League in Defence of Hong Kong's Freedom, as saying.
Despite the police violence the protesters continue to face, they vow to continue their actions.
"We'll keep coming back," said student Angel So.
AFP has video: