TBILISI (AFP) -- Voters in the Caucasus mountain state of Georgia go the polls Sunday for a parliamentary election seen as a referendum on the rule of veteran President Eduard Shevardnadze, the man blamed by many here for a decade of corruption and misrule.

But attention was focused on the hours after polling stations close, with opposition parties claiming the government planned to rig the election to limit the scale of its defeat, and warning that if that happened, thousands of voters would march on government offices in protest. "The government has never been so unpopular," said one opposition party leader, Mikhail Saakashvili. "The prospects for Shevardnadze's rule, if there is an attempt to rig the elections, look extremely bleak."

Anticipating trouble, police and troops have been put on heightened alert and had their leave cancelled, while the government has said it will come down hard on any civil unrest.

The election has added significance because rival opposition leaders are using it as a warm-up to the presidential election in 2005, when Shevardnadze will step down.

Georgia, a former Soviet republic of some five million people wedged between Russia and Turkey, is soon to assume strategic importance for the West.

The country lies on the route of the Baku-Tbilisi-Ceyhan oil pipeline, which is being built by a consortium of Western oil majors, with US backing, to export Caspian Sea crude to world markets.

A land of vineyards and fertile fields which used to have the highest per capita income of any Soviet republic, Georgia has slipped into poverty since it became independent in 1991.

The average Georgian has to get by on 50 dollars a month, unemployment is high and people suffer the indignity of frequent power blackouts.

"Georgians, who pride themselves on being a very sophisticated and educated nation, have come closer to African standards," Saakashvili said in an interview with AFP.

Shevardnadze has pointed to figures which show the economy perking up. "Unlike some people who think only of elections, we continue to regard the country's economy as our top priority," he said this week.

But opinion polls suggest voters have lost faith in him. Four opposition parties are jockeying for the lead while the pro-government For a New Georgia bloc is trailing with a popularity rating languishing around the six percent mark.

If Sunday's voting follows that pattern, Shevardnadze's administration would lose its majority in parliament and struggle to get any of its programmes approved.

But critics say the authorities -- who have a record of running dubious elections -- will use fair means or foul to make sure that does not happen.

Dozens of opposition activists have been beaten up and on Saturday, an explosion was reported outside an opposition office in southern Georgia.

An immediate concern is what will happen if voters take to the streets of Tbilisi to protest the result.

Analysts say, Shevardnadze could be vulnerable. The last time there were mass protests, when tax police tried to take a private television station off air two years ago, Shevardnadze had to cave in and sack several of his ministers.