Violent protests of disputed elections spread Friday from the capital to other parts of Ethiopia, leaving four people dead. Prime Minister Meles Zenawi vowed to prosecute opposition officials, who he said were responsible for the bloody clashes this week, state media reported.

Police have killed at least 40 people since the confrontations began Tuesday in Addis Ababa, the capital, medical officials said. The medical workers spoke on condition that they not be identified for fear of retaliation. Government officials put the number of dead this week at 24 civilians and seven police officers.

The protesters have called for an independent investigation into the killings in the capital and the release of political prisoners, according to witnesses.

Protests erupted Friday in Dessie, Gondar, Bahar Dar, Arba Minch, Awassa and Dire Dawa -- towns north and south of the capital that are mainly pro-opposition , according to diplomats, hotel owners and tour operators.

Four people were killed and 11 were wounded in Bahar Dar, a tourist site northwest of Addis Ababa, state TV reported, although the figures could not be immediately verified. Meles told state media that the main opposition Coalition for Unity and Democracy was responsible for the violence during the protests. Opposition officials would be charged in court, he said.

Diplomats from four European countries said Friday they had reports from opposition members and other contacts of police rounding up suspected opposition supporters overnight.

An estimated 3,000 people have been detained, according to the diplomats, who spoke on condition of anonymity because they wanted to avoid jeopardizing relations with the government. The diplomats acknowledged that it was not possible to obtain an exact figure.

Ambassadors from 21 countries that donate large sums of money to Ethiopia issued a statement expressing concern about the violence. They called for an immediate investigation and recommended that all political detainees be charged or released.

The violence erupted over disputed May 15 parliamentary elections. The vote gave Meles's Ethiopian People's Revolutionary Democratic Front control of nearly two-thirds of parliament. Opposition parties say the election and vote count were marred by fraud, intimidation and violence.