Umbrellas are seen left behind by protesters after police fired tear gas in an attempt to disperse them during a demonstration in the district of Yuen Long. Anthony Wallace/AFP/Getty Images

Fewer than 50 demonstrators now remain in Yuen Long station, following today's large-scale protest.

Riot police forced protesters to retreat to the station after trying to clear crowds for more than four hours. Police have now surrounded the building as the final demonstrators slowly begin to leave.

The authorities took strong action against the Saturday protest which was earlier declared illegal, having not been officially authorized by the police.

Both pepper spray and rubber bullets were used to disperse the crowd, which at its height organizers claimed numbered more than 100,000.

But it was a baton charge by riot police into the station as the protest drew to an end which is likely to become the defining image of the demonstration, with protesters comparing it to the events of last weekend when commuters in Yuen Long were attacked by alleged gang members.