Riot police armed with clubs clashed with a crowd of protesters demonstrating Saturday against the disputed election that kept Belarus' hard-line President Alexander Lukashenko in power.

The violence erupted when a gauntlet of black-clad officers blocked a march on a jail holding demonstrators arrested at previous protests over the March 19 presidential election, which the U.S. and European Union criticized as undemocratic.

Police began beating their shields with truncheons, then advanced on the crowd. Four explosions were heard, apparently from percussion grenades set off by police.

Marchers began to disperse, yelling "Fascists," but police pushed into the crowd and detained about 20 people, including opposition leader Alexander Kozulin, and loaded them onto trucks. At least two people lay injured on the ground, and one was taken away by ambulance.

Earlier, rows of police blocked some 3,000 people from massing on central Oktyabrskaya Square as the government tries to stifle a week of unprecedented protests in the tightly controlled former Soviet republic. Demonstrators shouted "Shame!" and "Long live Belarus!"

On the other side of the huge square, the main opposition candidate in last week's election, Alexander Milinkevich, led a separate crowd away to a nearby park, where he announced "the creation of a movement for the liberation of Belarus."

"The authorities can only confront the striving of the people for change with persecution and violence," Milinkevich told the crowd, which grew to as many as 7,000 people.

Demonstrators held flowers, waved the red-and-white historic flag of the opposition and shouted "Mi-lin-ke-vich!" and "We are not afraid!"

"The people have come out today, they have come out in the face of truncheons, in the face of arrests," Milinkevich said. "The more the authorities conduct repression, the closer they bring themselves to their end."

But while he praised those who have protested the election, he acknowledged their numbers are not enough to defeat Lukashenko's government.

"We can be proud of what we have already done: Fear is vanquished," he said. "But today there are not 200,000 or 500,000 of us coming out into the square. If there were, they (the authorities) would run away from the country."

"We are starting work against dictatorship, and this work will sooner or later bear its fruit," he said.

The demonstrations came a day after police arrested hundreds during the storming of a tent camp in the square, which had been the focus of round-the-clock protests over Lukashenko winning a new five-year term in a ballot called a farce and fraudulent by the opposition.

Milinkevich, who officially received about 6 percent of the votes and wants a new election without the participation of Lukashenko, had been calling all week for a major demonstration Saturday marking the anniversary of Belarus' first independence declaration in 1918.

"We're not planning any violence, any taking of the Bastille. We want a peaceful demonstration," he said before the rally, standing with his wife and about 100 relatives of detained activists.

Police took no action against the park rally, and did not prevent people from joining it.

"I am tired of being afraid, and the fear is leaving me," said Yelena Sokolovskaya, 44, an accountant at the rally. She said the government's claims that the economy is thriving are "a lie — Milinkevich speaks the truth."

Protesters threw snowballs at a three-man crew from Belarusian state television, which has shown the protests in an extremely negative light, and shouted "shame on Belarusian television!"

The crowd began to disperse peacefully after opposition figures called for an end to the rally and said the next major demonstration would be April 26.

But at the urging of Kozulin, many demonstrators headed toward the jail and the clash with police ensued.

The top police official, Vladimir Naumov, said one protester suffered a light head injury and eight police officers were hurt. He claimed police did not set off the explosions and accused protesters of throwing rocks and bottles, charging that Kozulin called for the government's overthrow and Lukasenko's death.

He refused to say how many people were arrested.

"The situation is calm and I think it will remain that way," Naumov said.

Milinkevich called the march "a provocation" and sharply criticized Kozulin, saying there had been an agreement that demonstrators would disperse after the rally. "Kozulin decided to spoil this holiday for the people," Milinkevich told The Associated Press.

The two appeared together at a campaign rally shortly before the election, but they have had obvious disagreements after the election, in which official results gave Kozulin 2.2 percent of the votes.

The ballot set off an unprecedented protests, beginning with an election-night demonstration that drew some 10,000 people to Oktyabrskaya Square — an enormous turnout in a country where police usually suppress unauthorized gatherings swiftly and brutally.

The European Union and the United States said Friday that they will impose sanctions on Lukashenko, who they say has turned Belarus into Europe's last dictatorship since his first election in 1994. Both called for an immediate end to the crackdown on the opposition.

EU leaders said the bloc would take "restrictive measures" against Lukashenko, including a likely travel ban and a possible freeze of Belarusian assets in Europe. The White House said the U.S. would act in unison with the EU.

However, the measures seemed unlikely to influence Lukashenko, who despises the West and has allied with Russia. In a statement late Friday, the Foreign Ministry said that the sanctions had "no prospects" and that Belarus reserved the right to take retaliatory measures.