Police fired tear gas on Sunday to disperse thousands of anti-government protesters who had gathered in a central Hong Kong park but later spilled onto the streets, briefly barricading roads and spray-painting buildings.

Out in numbers before the demonstration began, the police intervened promptly when the rally turned into an impromptu march. Several units of police in riot gear were seen chasing protesters and several arrests were made.

A water cannon truck drove on central streets, flanked by an armoured jeep, but was not used.

Organisers had initially applied for a permit for a march, but the police only agreed to a static rally in the park, saying previous marches had turned violent.

Once protesters spilled onto the streets, some of them, wearing all-black clothing, barricaded the roads with umbrellas and street furniture, dug up bricks from the pavement and smashed traffic lights.