Hong Kong protests: Tear gas fired at unauthorised demonstrators

Police have used tear gas against demonstrators marching in Hong Kong.

The march had been banned by police who feared there would be violence.

The rally was planned to condemn an assault on pro-democracy protesters by armed masked men that took place last week.

Protesters had accused the police of turning a blind eye and colluding with the attackers - claims the police deny.

Hong Kong has seen seven weeks of anti-government and pro-democracy protests.

The BBC's Stephen McDonell reports.