Analysts had widely predicted that Zenawi would triumph in the polls, with some reports suggesting that opposition groups did not believe they had any chance of beating the incumbant coalition.
In the country's elections in 2005, a post-poll government crackdown on opposition protests led to the deaths of almost 200 people. Earlier on Tuesday, Zenawi called for international recognition of the povisional results to avoid fresh protests.
"The people's vote will not be overturned by foreign forces," Zenawi said. "Some of our foreign friends have disappointed us but that's in the past. We urge them now to give recognition to the people's vote. The politics of hate is out. Not one life should be lost in post-election riots."
His comments came after New York-based Human Rights Watch criticised Sunday's vote as corrupted by pre-election irregularities, including telling voters they could lose food assistance, public-sector jobs, loans and educational opportunities if they voted against the ruling party.
Al Jazeera's Andrew Simmons, reporting from the Ethiopian capital Addis Ababa, said that it is unclear what effect such criticisms will have.
"It depends on how the opposition parties decide to play their tactics," he said, adding that security forces were deployed on the streets. "There is some tension, especially with this EU provisional report."
According to provisional results, the ruling EPRDF and allies had scored a landslide victory, winning an overwhelming number of votes in nine out of 11 regions and cities declared so far.
But opposition parties condemned the election before the polls had even closed, saying the EPRDF had routinely intimidated and harassed critics in the days and months ahead of the election.
Final official results are due on June 21.