By Pavel Polityuk
KIEV (Reuters) - Hundreds of people rallied in central Kiev on Monday to protest against what the Ukrainian opposition says was vote-rigging by President Viktor Yanukovich's ruling party in the October 28 parliamentary election.
Crowds gathered outside the Central Electoral Commission headquarters in the Ukrainian capital in response to a call for protest by opposition parties, including that of jailed ex-prime minister Yulia Tymoshenko.
Police told the crowd by loud-speaker that the protest was illegal and might be broken up by force if people did not disperse, a threat ignored by the demonstrators.
"The Party of the Regions is simply stealing the votes of Ukrainians and registering them as the votes of the candidates of the party in power," said Arseny Yatsenyuk, who heads the united opposition in the absence of Tymoshenko.
"We have gathered here to defend our choice, the choice of Ukraine and Ukrainians. Ukraine has shown that it is capable of beating the Party of the Regions," he told the crowd.
Tensions have focused on the outcome of a handful of constituencies where the vote-count for seats in the 450-seat parliament has not been completed.
Anger erupted at several of nine disputed districts with election officials conducting the vote-count besieged by opposition supporters and members of Yanukovich's Party of the Regions, demanding a re-count or threatening court action. Riot police used tear gas to quell trouble in one district.
The opposition hinted it might go as far as boycotting the new parliament if it did not get satisfaction.
"Unless the government immediately stops rigging the vote and illegally taking away mandates won by opposition candidates ... United Opposition is ready to denounce the next parliament as powerless and insist on early parliamentary and presidential elections," it said in a statement.
From the vast majority of results already in, the Regions, seen as representing the interests of big business, appear to have retained a majority of more than 225 seats in the assembly, assuming support from their traditional communist allies and some independents.
But the Batkivshchyna (Fatherland) of Tymoshenko, which forms the core of the united opposition, has made a strong showing.
The opposition has been further re-energized by the UDAR (Punch) party of world heavyweight boxing champion Vitaly Klitschko and the far-right nationalist Svoboda (Freedom) party which have won representation in parliament for the first time.
"We are protesting. We want to defend our votes. The Party of the Regions has falsified the elections, taken our victory. It is us who ought to have the majority not them," said 50-year-old Nadezhda Storozhuk, a Batkivshchyna supporter.
"We have turned out to defend the interests of simple people who have voted and whose votes have been stolen. We are ready for other kinds of action if need be," said Yuri Derkach, 45, a supporter of Svoboda.
(Writing by Richard Balmforth and Olzhas Auyezov; Editing by Jon Boyle)