The killings occurred when security forces opened fire on Wednesday to scatter hundreds of demonstrators who formed makeshift barricades, hurled rocks and smashed windscreens in protest against a May poll the opposition says was rigged.
The government said two police officers were killed and 54 other officers wounded in the violence, which follows months of tensions between the government and opposition in sub-Saharan Africa's second most populous nation.
Information Minister Berhanu Hailu said only 11 protesters were killed, calling higher figures exaggerated, and said "hooligan" opposition figures were behind the unrest in the city, a bastion of opposition to Prime Minister Meles Zenawi.
Sources, contacted at five city hospitals, said women and youths were among those killed on Wednesday. The violence, the second straight day of unrest in the capital, brings to 31 the number killed in the past two days.
The opposition is disputing
Meles's victory in May polls
Many of the wounded had been shot in the upper body, medical sources said.
"We are protesting because the government stole the election. People are angry because the police are very cruel," said Ghebremichael Ayele, dragging pieces of wood to block a road leading to the capital's biggest hospital.
Hundreds of heavily armed riot police were deployed across the capital on Wednesday amid heavy machine-gun fire, rifle fire and loud explosions.
The fighting spread across the city, reaching the doorsteps of the embassies of Britain, France, Kenya and Belgium. Workers at UN headquarters were told not to leave their offices.
The violence followed clashes on Tuesday between protesters and police that resulted in the deaths of eight people and injuries to 43 others.
The clashes erupted after the arrests on Monday of 30 taxi drivers who took part in demonstrations against the 15 May parliamentary elections.
The elections gave Meles's Ethiopian Peoples Revolutionary Democratic Front control of 60% of the Ethiopian parliament.
Tensions turned into deadly
violence in the capital
Opposition parties made strong gains, but say the vote and
counting were flawed by fraud, intimidation and violence.
They claim the ruling party rigged the elections.
The violence flared again after sporadic bursts of gunfire in parts of Addis Ababa late on Tuesday and early on Wednesday, hours after security officials arrested the leaders of the main opposition party.
Security officers have arrested all 15 members of the Coalition for Unity and Democracy's central committee and about 1000 supporters, a lawyer who works for the opposition party said on condition of anonymity.
Opposition spokesman Gizachew Shiferaw urged supporters to stay calm and accused police of using excessive force.
At least 42 people were killed by police during protests in June, according to human rights groups.