Protesters said the government had failed to tackle corruption

Braving heavy rain, they gathered in the city's central square, near the presidential and government offices.

Many chanted "Down with thieves", demanding that President Kurmanbek Bakiyev deal with corrupt officials.

Mr Bakiyev unexpectedly addressed the rally, saying the reforms he pledged would take time to have an effect.

Mr Bakiyev won a landslide victory after the Kyrgyz revolution last year.

But the protesters complained that they had seen no improvement in their standard of living since then, the BBC's Ian McWilliam in Bishkek reports.

'Irresponsible politics'

The rally was organised by opposition parties and civic groups, who demanded that President Bakiyev follows through his reforms.

Mr Bakiyev (right) said it was impossible to change "everything overnight"

The demonstrators - many carrying placards and national flags - also accused the government of failing to tackle what they described as widespread corruption in the impoverished Central Asian state.

"I'm not happy with our president. He is not keeping his promises," Gulnara Zhainakova told the Associated Press news agency.

During the rally, President Bakiyev unexpectedly arrived along with Prime Minister Felix Kulov, our correspondent says.

He told the crowd that reforms required time to take effect and that what he called irresponsible politics would not help.

Riot police in full gear patrolled the peaceful rally which ended after about two hours.