MINSK, Belarus - Thousands of opposition supporters in Belarus tried to storm the main government building to protest what the opposition claims was large-scale vote-rigging in Sunday's presidential election.

Dozens of protesters were injured in clashes with riot police, left bruised and bloody after being beaten with clubs.

About 40,000 opposition activists rallied in central Minsk to call for the country's longtime authoritarian leader, Alexander Lukashenko, to step down. It was the largest opposition rally since 1996.

"We had a peaceful protest, and it is the authorities who used force," said Marat Titovets, 40, an engineer.

Leading opposition candidate Vladimir Neklyayev was beaten by riot police while leading a few hundred supporters to the demonstration and was taken by ambulance to a hospital, his wife said.

After the polls closed, opposition activists converged as planned on October Square, but most of the square had been flooded to make an ice-skating rink, and pop music boomed from loudspeakers.

The protesters then set off along the main avenue toward Independence Square, where the main government building is situated.

They shouted "Leave!" to Lukashenko, who has led Belarus since 1994 in a heavy-handed regime often called the last dictatorship in Europe.

Russia and the European Union closely monitored the vote, having offered economic inducements to tilt Belarus in their direction.

Although once seen as almost a lap dog of Russia, Lukashenko, 56, recently has quarreled with the Kremlin as Russia raised prices for the below-market gas and oil on which Belarus' economy depends.

But his tone changed this month after Russia agreed to drop tariffs for oil exported to Belarus, a concession worth $4 billion a year.

Lukashenko also is working to curry favor with the West, which has harshly criticized his years of human-rights abuses and repressive politics. Last week, he called for improved ties with the United States, which in previous years he had cast as an enemy.

Lukashenko, a Soviet-era collective manager, maintains a quasi-Soviet state, allowing no independent broadcast media and keeping 80 percent of industry under state control.