Nine bombs exploded across Ethiopia's capital, killing four people and injuring more than 42 others in what police said was a coordinated attempt to discredit the government.
No group immediately took responsibility for Friday's blasts, which focused on government-owned companies and public transportation. But the bombings could point to growing militant opposition to the government.
The attacks came days before the anniversary of last year's general election on Monday. International observers had called the balloting seriously flawed and opposition politicians have refused to take up their posts to protest what they called government rigging.