Police in Slovakia have fired tear gas and water cannon in the capital to disperse about 100 anti-government protesters following a mostly peaceful demonstration against high-level corruption.

For the second time this year, allegations about corruption that appeared online caused anti-government protests in Bratislava and for the first time in other major cities.

Several thousand people rallied in Bratislava and thousands of others demonstrated in seven other cities on Friday to demand that early elections planned in March be postponed to allow a thorough investigation.

In December, a file known as Gorilla - allegedly compiled by the country's SIS spy agency - appeared on the internet suggesting that the financial group Penta had bribed government and opposition politicians in 2005-06 to win lucrative privatisation deals.

Police are investigating the allegations, but SIS has not confirmed the document's authenticity, and Penta and politicians named in it have denied wrongdoing.

After the demonstration in Bratislava, about 100 protesters tried to storm parliament and threw cobblestones at riot police, who used water cannon and tear to repel the crowd. Three police officers were injured and four radicals were detained, police spokeswoman Petra Hraskova said.

Earlier, some protesters pelted eggs and bananas at the government's offices and the seat of the president.

Organisers called the protest a success and said others may follow. In other cities, the protests ended without any violence.

A similar anti-government protest took place in January.