The ruling party, Zanu-PF, says it is ready to peacefully concede defeat in the event that it loses the presidential elections, whose results are expected soon.
The hopes of a new chapter for Zimbabwe after years of violence and dissent are being dashed following the chaos that rocked the country on Wednesday killing at least three people.
Zimbabwean President Emmerson Mnangagwa says the government is surprised by violence that broke out after the announcement of National Assembly results.
The commission said it would release vote totals "sometime" on Thursday, even though it said most of the results "are here with us".
The head of the Commonwealth election observers in Zimbabwe is condemning what he calls the "excessive use of force against unarmed civilians" by security forces.
Mr Chamisa's party alleges that the elections are being rigged in favour of Zanu-PF, a claim ZEC denies.
Home Affairs Minister Obert Mpofu accused the opposition of using the presence of global election observers to "grandstand" and cause "anarchy".
As Zimbabweans waited on tenterhooks to learn the victor of the country's presidential election, a deadly crackdown on opposition protesters in the capital spurred fears of a return to the days of authoritarian rule under Robert Mugabe.
By the end of the day, three people were dead, several injured, and visible blood pools stained the Capital's street, marking the end of a very bad day.
Tendai Biti, a candidate for opposition party Movement for Democratic Change (MDC), has accused the ruling Zanu-PF regime of plotting to assassinate himself and Chamisa.
On August 1 the election commission announces that ZANU-PF has won most of the seats in parliament. "We condemn in the strongest sense the action taken today", MDC spokesman Nkululeko Sibanda told reporters.
Zimbabweans protest in downtown Harare. All we know for sure is that one of them is lying.
"I will stay here until Chamisa is president", said Amandishe Muzhinji, who traveled back from Swaziland where he works as a migrant laborer to vote in Monday's election.
ZEC said the final results of the presidential race may not be known until Saturday.
TEN alleged MDC Alliance supporters were on Thursday arrested by police after they had sought refugee from the Morgan Richard Tsvangirai House, the MDC-T main headquarters in Harare on Wednesday.
"We've more votes that ED, we won the popular vote and we will defend it", he tweeted.
The 94-year-old former leader had been in power since independence from white minority rule in 1980 until he was forced to resign in November after the military and ruling party turned on him.
This descent into violence, bloodshed and unrest is unlikely to help the president in efforts to end Zimbabwe's worldwide pariah status.
It does not give the results for the presidential vote. The EU mission questioned why presidential votes were counted first but were being announced last.
"ZEC is taking its time to transmit results from polling stations to wards and to constituency centres, and this delay is totally unacceptable particularly in urban centres like Harare, Bulawayo, Gweru, Mutare and Masvingo", he said.