Many of the dead and injured had gunshot wounds
The Black Lion hospital in the capital, Addis Ababa, was full of those injured in the clashes, while crowds of relatives wept outside.
Hundreds of students have been arrested this week for defying a protest ban.
Final results have not been announced three weeks after the polls, as reports of massive fraud are investigated.
Opposition blamed
The police fired live rounds to disperse stone-throwing protesters in the Mercato and Piazza markets in the city centre.
Reporters said they had seen 11 bodies in the Black Lion hospital, four of which had bullet wounds in the head.
HAVE YOUR SAY When the crowd dispersed in fear, they started shooting at them. There was blood everywhere
Yosef, Addis Ababa
Eyewitness: Running from the police Send us your comments
The government said it regretted the loss of life, which it blamed on looters, incited by the opposition Coalition for Unity and Democracy.
"CUD, which is the perpetrator of the violence, will have to take responsibility," Information Minister Bereket Simon told the Reuters news agency.
The CUD has denied being behind this week's student protests.
Mr Bereket said that seven buses had been destroyed and businesses and banks damaged by looters.
He denied the police had used excessive force to restore order.
Leaflets
Doctors said they were treating at least 100 people, many of whom had been shot. Some of those who agreed to speak to journalists denied taking part in the demonstrations.
"I was looking for my son, I opened the door and I was shot," Ateneyesh Mamo, a mother of two who was shot in the pelvis, told the AFP news agency.
Protests began on Monday when some 500 students were arrested
"The police were running at the crowd, firing shots," said Getu, a 22-year-old labourer.
Earlier, taxi drivers had gone on strike, joining protests started by students on Monday.
The BBC's Mohammed Adow in Addis Ababa says thousands of leaflets had been distributed, calling for the strike.
On Tuesday, students threw stones at the police who responded by storming a technical college and arresting about 100 people.
The students were beaten with batons and rifle butts by police, who also fired shots in the air, witnesses said.
On Monday, about 500 people were arrested and a girl died in clashes which began when students defied the 30-day ban on protests which was announced after the poll.
Human rights
The British Foreign Office has warned citizens travelling in Ethiopia to be cautious and says that tension is spreading to other towns and cities.
Ethiopian Prime Minister Meles Zenawi is a member of the UK-led Commission for Africa, which promises to improve governance and respect for human rights in Africa, in return for more western aid, debt relief and better terms of trade.
According to provisional election results, the ruling Ethiopian People's Revolutionary Democratic Front (EPRDF) and its allies have won 320 seats so far, giving it a majority in the 547-member parliament.
The opposition have, however, won almost 200 seats - a huge gain from the 12 they had in the previous parliament.
EU observers have voiced concern over irregular vote counting and biased reports by the state-owned media.
Bei Protesten gegen die Regierung kamen in der Hauptstadt Äthiopiens mindestens 22 Menschen ums Leben, als die Polizei das Feuer auf Steine werfende Demonstranten eröffnete.

Korrespondentenberichten zufolge befinden sich im „Black Lion Hospital“ in Addis Abeba zahlreiche Menschen, die bei den Zusammenstößen verletzt wurden. Behandelt würden vor allem Schussverletzungen. Oppositionsanhänger, in der Mehrzahl Studenten, demonstrieren seit drei Tagen in Addis Abeba und anderen großen Städten des Landes gegen das provisorische Wahlergebnis der Parlamentswahl. Regierungsvertreter machen die größte Oppositionspartei „Koalition für Einheit und Entwicklung“ (CUD) für die Eskalation der Gewalt verantwortlich. Das auswärtige Amt rät dazu, „nicht notwendige Reisen nach Äthiopien zu verschieben“.

Die regierende „Ethiopian People's Revolutionary Democratic Front“ von Ministerpäsident Meles Zenawi hat dem Ergebnis zufolge zusammen mit verbündeten Parteien 328 von 547 Sitzen gewonnen. Die Oppositionsparteien kommen laut vorläufigem Ergebnis auf 194 Sitze. Bei den letzten Parlamentswahlen vor fünf Jahren gewannen die Oppositionsparteien lediglich zwölf Sitze.

Aufgrund zahlreicher Beschwerden wurde die für heute geplante Veröffentlichung des Endergebnisses um einen Monat verschoben. Bei der Wahlkommission gingen Beschwerden aus mehr als der Hälfte der Wahlkreise ein. Kemal Bedri, Vorsitzender der Wahlkommission, begründete auf einer Pressekonferenz die Verschiebung der Veröffentlichung der Ergebnisse mit dem Ausmaß der Beschwerden. Zeitgleich wurden einige hundert demonstrierende Studenten auf dem Gelände der größten Universität von Addis Abeba verhaftet. Ministerpäsident Meles Zenawi hatte nach der Wahl ein einmonatiges Demonstrationsverbot verhängt.

Internationale Wahlbeobachter dokumentierten Unregelmäßigkeiten, kamen aber zum Ergebnis, dass die Wahl freier war als die Parlamentswahl des Jahres 2000. Besonders kritisiert wurde die unausgewogene Berichterstattung der staatlich kontrollierten Medien.