At least 22 people were killed and more than 100 wounded when Ethiopian security forces fired into crowds Wednesday in a third day of unrest over disputed elections last month.

Ethiopian authorities said police and troops opened fire on stone-throwing protesters who were looting shops, robbing banks, attacking police officers and trying to free detainees. The government blamed the main opposition group, the Coalition for Unity and Democracy, for inciting the violence.

State television put the death toll at 22.

"The government regrets very much" the deaths, Information Minister Bereket Simon said. The opposition coalition, "which is the perpetrator of the violence, will have to take responsibility."

An unknown number of opposition leaders were reportedly placed under house arrest.

A spokesman for the opposition denied it had anything to do with the violence or a strike by taxi drivers that began Wednesday and severely hampered transportation in Addis Ababa, the capital.

"The people said, 'Enough is enough,' " said Bebebe Eshetu, the spokesman.

Witnesses said police fired indiscriminately. Others said some people were taking advantage of the situation to loot and attack passersby, Ana Gomes, the chief European Union observer monitoring the elections, said at a news conference.

U.N. Secretary General Kofi Annan condemned the killings and appealed for calm. "The secretary general is seriously concerned about the tense situation," a U.N. spokesman said.

During the clashes, gunfire could be heard across the capital. Most shops were closed.

At hospitals in the city, hundreds of relatives wept in packed, blood-spattered wards as a steady stream of ambulances brought in more dead and wounded.

One witness said police opened fire as he stepped from his house into the street with his brother, who was hit and injured. The ruling party "is killing us because we didn't vote for them," said the man, who gave his name only as Teopros.

The shootings followed two days of student protests and weeks of rising tension over preliminary results from the May 15 parliamentary elections, which the opposition says were rigged by Prime Minister Meles Zenawi's ruling party, the Ethiopian People's Revolutionary Democratic Front.

The government imposed a month-long ban on public demonstrations after the elections and said troublemakers would be dealt with sternly. Hundreds of police officers and paramilitary troops have flooded the capital to enforce the ban.

"Police have been authorized to take appropriate action against those who attempt to disrupt the peace," Ethiopian state television said in a statement.

Preliminary results show that the ruling party, which has governed the country for 14 years, and its allies won enough seats to form the next government, but with a sharply reduced majority. Final results are due July 8.

Observers considered the vote a test of Ethiopian democracy. Meles overthrew Mengistu Haile Mariam in 1991, ending 17 years of Marxist rule. The U.S. government has touted Meles as one of the more progressive leaders in Africa and a key partner in the war against terrorism.

Diplomats have said the election was the most democratic in Ethiopia's 3,000-year history. But the E.U. criticized the ruling party for using the state-owned media to shut out the opposition and said there had been irregular vote counting.

The opposition has accused government agents of intimidating and killing some of its officials, and international human rights groups have accused the government of widespread abuses.

Opposition groups also accuse Meles of failing to lift Ethiopia out of chronic poverty. They have advocated a bigger role for free markets in this country of 72 million in the Horn of Africa.

The ruling party has denied the allegations of harassment and vote-rigging and accused the opposition of fomenting protests in defiance of the demonstration ban.

Ethiopians arrive at a hospital in the capital, Addis Ababa, to search for relatives after security forces opened fired on demonstrators.