Zimbabwe's main opposition party called on Friday for nationwide protests and a re-run of elections that it said fraudulently handed President Emmerson Mnangagwa a second term in office.

The appeal from the Citizens Coalition for Change (CCC) came a day after Mnangagwa said the vote was valid and warned there would be a crackdown on anyone spreading chaos.

"I warn anybody who may want to bring any chaos in this country we are ready," he said during a ceremony to open a lithium plant. "Whoever shall preach hate speech will be responsible for their hate speech, our prisons are not full."

The electoral commission said late on Saturday Mnangagwa had secured roughly 53% of the vote, leaving CCC leader Nelson Chamisa in second place on 44%. Mnangagwa's ruling Zanu-PF party was named winner of the parliamentary election but fell just short of the two-thirds majority needed to change the constitution.

Analysts have questioned the credibility of the elections, which were marred by arrests of vote monitors. Zanu-PF has said there were no irregularities and Mnangagwa has urged anyone with complaints to go to the courts.

The CCC has accused Zanu-PF of suppressing the vote in areas where it polls well, but has so far not lodged a legal complaint.

On Friday it called for protests in Zimbabwe's 10 provinces and asked activists to launch online campaigns and share evidence of voting malpractice.

"We are encouraging people to behave in a peaceful manner. The protests are up to the people. We just want their vote to find expression," CCC spokesperson Promise Mkwananzi told Reuters.

The CCC wants other African countries to intervene and mediate in its dispute with the ruling party, but analysts say its chances of overturning the election results via the courts are slim given the judicial system is viewed as being controlled by Zanu-PF.

The CCC has seven days from the results declaration to lodge a court appeal.