Nine bombs exploded in Ethiopia's capital Friday, killing three people and wounding 42, a police spokesman and witnesses said.

The bombs were concentrated on government buildings and public transportation. A police spokesman said the bombings were clearly coordinated by one organization, but he refused to name what group may have carried out the attacks and no one claimed responsibility.

CountryWatch: Ethiopia

The bombings came just before Monday's anniversary of last year's general election. International observers called the balloting seriously flawed and opposition politicians have refused to take up their posts in protest of what they called government rigging.

Police have blamed other small bombings in recent months on alleged militant elements of the political opposition. But with no indication beyond police statements that they were politically motivated, some in the capital have questioned that theory. The previous small bombings have rarely caused injuries or caused significant damage and were not accompanied by any claims of responsibility.

"We believe the main target of these bombings are the civilians and it is being done intentionally to give an impression that there is no peace or stability in Addis Ababa," Demsash said.

Four bombs exploded in the morning, another four exploded after midday. The bombs struck across the city, but four exploded in Addis Ababa's busy Mercato, the main shopping district.

One of the morning bombs exploded outside two cafes in the Mercato, killing two people and injuring seven — five of them seriously, witnesses said. A third man was killed in the afternoon when a bomb destroyed the rear of a small bus, an Associated Press reporter at the scene said.

Federal police spokesman Commander Demsash Hailu said 16 people were injured in that blast.

The first blast occurred at 4:50 a.m. in one of Addis Ababa's main plazas and damaged an Ethiopian Airlines office, but caused no injuries.

The next three blasts occurred between 9:20 a.m. and 9:40 a.m. One damaged the headquarters of the city's electricity company, injuring seven. The next blast blew out the front of a city bus, injuring seven, witnesses said. Then a bomb detonated outside the cafe.

The second afternoon blast destroyed a minibus taxi in front of a secondary school, witnesses said, but there were no immediate reports of casualties.

Two more bombs detonated near the bus station in the Mercato, one in a public toilet inside a hotel and the second outside of a barbershop. The hotel bombing injured three, the second one injured two, including the barber. A ninth bomb that later detonated under a bridge caused no injuries or significant damage.

"We were taking our lunch and there was a small explosion," the barber's wife, Alem Asfaw, said.

At the Amico Cafe in the Mercato, 15-year-old Bereket Betiwibid described seeing patrons knocked out of their chairs and two waitresses thrown across the verandah when the bomb exploded on the sidewalk outside. Tiny holes dotted the walls where bomb fragments appeared to have hit.

Dr. Daniel Getenet, at Black Lion Hospital, said five seriously injured patients were brought in and had been stabilized, but they are still being examined for suspected internal injuries.

Genet Wordofa, sitting in the hospital next to her badly injured adult son, said she was about to get on the bus when it exploded in the morning.

"I was shocked because we had just returned from a checkup at a nearby clinic and was about to get on the bus when the explosion occurred," she said. "All of a sudden my son was on the ground bleeding."

The son, Metike Ayelegine, suffered a chest injury and his hand was mangled in the explosion.

Groups often blamed for such acts include the Oromo Liberation Front and the Ogaden National Liberation Front, two groups fighting for greater autonomy for their regions. Both groups, though, have quickly claimed responsibility for attacks outside of Addis Ababa in the past. Agents from neighboring Eritrea are also frequently blamed.