WARSAW (AFP) - Several thousand Polish opposition supporters marched in the capital Warsaw on Saturday to denounce alleged irregularities in last month's local elections.

The 2km march took the protesters, waving Poland's red and white flag, past the government seat and ended at the monument to independence father Jozef Pilsudski.

"It's a march of citizens defending democracy, press freedom and civic rights," Jaroslaw Kaczynski, head of the conservative opposition Law and Justice (PiS) party, said at the start of the protest.

Major computer breakdowns disrupted the first round of the local elections, prompting the opposition to cry foul, noting wide differences between voter surveys and the announced results.

The ruling Civic Platform swept most of Poland's big cities including Warsaw, Gdansk, Wroclaw and Poznan, while the PiS held onto power in smaller cities, mainly in the east and south-east.

Coming six months before a presidential election and a year before parliamentary polls, the local vote was seen as an important test for the ruling party.

Since Saturday's protest coincided with the 33rd anniversary of a crackdown by communist leader Wojciech Jaruzelski on the Solidarity trades union, the demonstrators read out the names of dozens of people killed during the period of martial law that began with the December 1981 crackdown and ended in July 1983.