Election officials said the majority of the voters who took part in last week's election cast their ballots in favor of Robert Mugabe, in office since the 1980s.
Ashton said the EU "takes note" of the announcement and welcomes the peaceful atmosphere in which the elections took place.
A monitoring group from Zimbabwe said there were problems with the polls, saying at least 1 million people were unable to take part in last week's contest. The African Union, however, said it observed few irregularities.
"The EU is concerned about alleged irregularities and reports of incomplete participation, as well as the identified weaknesses in the electoral process and a lack of transparency," Ashton said in a Saturday statement.
Her comments were echoed by British Foreign Secretary William Hague, who said he had "grave" concerns about the election.
Mugabe secured a seventh four-year term in office with more than 60 percent of the vote. Challenger and Prime Minister Morgan Tsvangirai called the presidential election fraudulent and vowed to contest the results.