Police charged into crowds at Addis Ababa University to grab protesters and beat others with batons in the first public protest against the May 15 elections.

The army's special forces troops stood by, armed with assault rifles and rocket propelled grenades. Riot police with tear gas and a water cannon also stood by as regular police quelled the demonstration.

Demonstrations have been banned and the capital police placed under Prime Minister Meles' control since election day. Meles' party retained control of parliament according to official but not yet ratified results, but opposition parties have alleged widespread election fraud.

Police detained an estimated 500 protesters who were chanting: "We are only students, we are not an army." Police and government officials refused immediate comment.

Hundreds of police officers had sealed main roads leading into the capital's university. The elections had been seen as a test of Meles' commitment to reform his sometimes authoritarian regime. Before questions surfaced about the count, EU observers had called the campaign and voting stages "the most genuinely competitive elections the country has experienced," despite some problems and human rights violations.

Clashes spread to other campuses around the city later Monday, with police opening fire with tear gas on students at a teacher training college. The capital has a number of university campuses with a total of some 20,000 students.

Minister of Information Bereket Simon, who is also spokesman for the ruling Ethiopia People's Revolutionary Front, said the main opposition Coalition for Unity and Democracy is behind the protests.

"They have been preaching violence, and now they are instigating it. The responsibility for what has happened falls on their shoulders," Bereket told The Associated Press, adding authorities are considering taking legal action against the party.

Berhanu Nega, vice chairman of the Coalition for Unity and Democracy, denied the charges, saying the party had urged students to hold off protests.

"Our worry is that the ruling party will use these protests as an excuse to crack down and resort to force," Berhanu said.

The party was getting reports that protests also occurred in Awassa in southern Ethiopia and Gonder, in the north, Berhanu said.

Bereket said not a single police officer or student had been injured, but pictures taken by an Associated Press photographer and others showed officers hitting students with the butts of assault rifles and bloodstains on the ground.

Ethiopia's political parties are challenging the results of 55 percent of the races, electoral chief Kemal Bedri said Monday, acknowledging the outcome of the vote could be affected by investigations into those complaints.

Kemal said investigations would determine whether it was necessary to hold a repeat vote for the 299 disputed seats before July 8, when full, ratified results are expected to be released. They were originally set for release Wednesday.

The ruling party has so far won 302 seats and its allies garnered 26, according to the provisional results released so far.

Opposition parties won 194 seats in the 547-seat lower house of parliament. They won only 12 seats in the last election in 2000, which was not followed by protests because the opposition was weak then.

The opposition and ruling parties have alleged gunmen intimidated voters, people were forced to vote for certain parties, ballot boxes were stuffed or disappeared and the number of ballots in some constituencies exceeded the number of registered voters.

Representatives of political parties and the National Electoral Board will investigate the complaints and observers from the African Union, European Union and the Carter Center will be invited to monitor the process, Kemal said.

Ethiopia was an absolute monarchy under Emperor Haile Selassie until the mid-1970s, when a brutal Marxist junta overthrew him.

Civil wars wracked the ethnically fractured country in the 1980s, and famine took as many as 1 million lives. The current ruling group overthrew the junta in 1991.