"We say the election took place without our observation, and that means if our observers have not participated, the voting day has been compromised," he said.

Hailu Shewal, leader of the All Ethiopia Unity Party went further. He said reports from his party's field workers indicated a 'disastrous situation', with opposition observers forced to flee in many places, and ruling party cadres marching voters into the voting booths and watching to see how they voted.

The 74-year-old veteran political leader said he is disgusted at the extent of the rigging, and vowed to quit politics.

"I am not participating in a ridiculous election. Never again," he said. "Maybe people think I am committing suicide, but politics is not my life. I am not in the business of cheating."

The European Union and the African Union had about 240 observers spread across the country monitoring activities at 43,000 polling stations. After the polls closed, chief EU observer Thygs Berman called the election 'peaceful and quiet', but acknowledged there had been complaints of vote rigging.

"It is about of course the technical errors. But there are more," Berman said. "There are complaints by political parties, there are complaints by candidates. We will see in the coming hours and days how we shall evaluate these complaints."

Berman said he had heard no reports of election-related violence.

Opposition leaders said despite the possibility of a crushing defeat they would not call their supporters into the streets to protest.