Protesters clashed with police in Hong Kong on Saturday as thousands rallied in spite of a police ban on demonstrating.

Police put blue dye in water cannons, intended to stain protesters and mark them out for arrest later.

The Hong Kong protests, sparked by a proposed extradition bill from mainland China, have been going on for 13 weeks.

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As flash points erupt between protesters and police in Hong Kong, water cannons filled with blue dye are being turned on the protesters.

Hong Kong citizens were out en masse protesting for the 13th week in a row on Saturday, despite a police ban on rallying. The protests were sparked in June by a proposed extradition bill by mainland China.

There were flashpoints between the police and protesters on Saturday, with the police deploying tear gas and water cannons, while protesters threw bricks and Molotov cocktails, setting fire to barricades.

Police officers walk past a burning Molotov cocktail. REUTERS/Tyrone Siu

Police put blue dye in the water cannons directed at protesters, coating the road in a blue wash. The dye is intended to stain protesters and mark them out for later arrest.

Protesters are engulfed in a spray of blue dye. PHILIP FONG/AFP/Getty Images

Several prominent activists were arrested on Friday ahead of Saturday's protests, although two were subsequently released on bail. One of the arrested activists, Agnes Chow, shared pictures of the blue jets of water.

—周庭 Agnes Chow Ting (@chowtingagnes) August 31, 2019

Last week Hong Kong police said it had arrested 86 protesters, including a 12-year-old.

A report emerged earlier this week that Beijing had refused to scrap the extradition bill that sparked the protests 13 weeks ago.