"The electoral commission failed to meet the mark in a number of ways and the election failed to meet the mark in a number of ways", said Johnnie Carson, a former USA assistant Secretary of State for Africa, who is part of an observer mission from the International Republican Institute and the National Democratic Institute.
A voter in Harare said Zimbabwe was eager to hear the election results as soon as possible.
The Zimbabwe Electoral Commission has announced 110 seats for Zanu-PF so far, and 41 for MDC Alliance, ZBC state media reported.
The remaining winners were still to be declared. For future reference, the Zimbabwe Electoral Commission can embrace the electronic voting system because it is quicker and transparent and everyone who is eligible to vote can cast their vote even from overseas, rather than the ballot system where people have to go to the polling stations and queue. But he also criticized the election commission's "lack of transparency", and "some problems around polling stations" on voting day.
Basically Zanu PF has won the two-thirds majority and thus has the power to change the constitution if need arises.
Mugabe's 37-year rule ruined the country's economy and left it isolated on the worldwide stage, so authorities are hoping that a credible election could herald a new era for the country and bring back foreign investment and prosperity.
MDC leader and presidential candidate Nelson Chamisa, who has alleged vote rigging, said on Twitter that he was confident of victory.
He said it was his fervent hope that the peaceful environment would continue after the elections.
Thousands of supporters of the opposition Movement for Democratic Change chanted anti-government slogans in Harare and faced off against a heavy police presence, fearing that their candidate, Nelson Chamisa, would have the election stolen from him.
Ballots are still being counted in the presidential election with results expected to be announced later this week.
Both the European Union and US observer missions urged the release of the presidential results as soon as possible, with the lead observer for the USA team, former Liberian leader Ellen Johnson Sirleaf, warning that "the more the presidential vote is delayed, the more it calls into question the population's confidence in the election process".
Overseas election monitoring teams are to issue their reports on the parliamentary and presidential poll on Wednesday. One independent candidate and a member from a party linked to Mugabe also won one seat each.
Supporters of the opposition Movement for Democratic Change party react as they block a street in Harare, Zimbabwe.