Hong Kong police have briefly used water cannons against anti-government protesters after firing tear gas during clashes with protesters throwing bricks yesterday for the first time in more than a week.

Protesters threw at least one incendiary bomb and some set off on narrow side streets not covered by showers of water cannon, which had not been used for years during anti-government protests.

The railway company in the Chinese-ruled city had stopped some services in a bid to prevent people from gathering, but protesters demanding democracy in the former British colony arrived at a sports stadium in the port of Kwai Chung and set off for nearby Tsuen Wan.

Some snatched bricks from the pavement for use in clashes that spread in many directions. Police had earlier warned that they would start an "operation to disperse" the protesters and asked people to leave. Hundreds remained for a long time after sunset and discussed what to do next.

Protesters say they are fighting the decline of the "one country, two systems" arrangement under which Hong Kong returned to China in 1997 with the promise of continuing the freedoms the mainland has not enjoyed for 50 years.