About 400 people were arrested in New Year's Day protests in Hong Kong after what started as a peaceful pro-democracy march of tens of thousands spiralled into chaotic scenes with police firing tear gas to disperse the crowds.

The tension on Wednesday came about after some arrests were made in the Wan Chai bar district, which has been the target of protesters anger in recent weeks.

When scuffles broke out, large numbers of black-clad protesters rushed to the scene while other protesters formed human chains to pass them various supplies including bricks, forcing police to bring in their own reinforcements.