Early parliamentary results in Zimbabwe showed the ruling party and the main opposition in a close race on Friday, after an election in which President Emmerson Mnangagwa's ZANU-PF party was widely expected to maintain its 43-year grip on power.

Results announced so far by the Zimbabwe Electoral Commission showed ZANU-PF winning 43 parliamentary constituencies and the main opposition party Citizens Coalition for Change (CCC) winning 37, out of a total of 210 single-member constituencies.

Presidential results have yet to be announced after Wednesday's vote, which was extended into Thursday in some neighbourhoods due to late printing of ballot papers.

Mnangagwa, 80, is seeking re-election at a time when the southern African country is grappling with soaring inflation and high unemployment, with many Zimbabweans reliant on dollar remittances from relatives abroad to make ends meet.

His main challenger is 45-year-old lawyer and pastor Nelson Chamisa.

Zimbabwe's chances of resolving a debt crisis and obtaining World Bank and International Monetary Fund loans are at stake, as foreign lenders have said a free and fair vote is a pre-condition for any meaningful talks.

The government and the electoral commission have promised a clean election, but some political analysts have said it is likely to be heavily skewed in Mnangagwa's favour, based on his party's history of using state institutions to manipulate results.

The Southern African Development Community's (SADC) election observer team said that the voting was peaceful, but that there were issues including voting delays, the banning of rallies, biased state media coverage and the failure of the electoral commission to give candidates access to the voters' role.

"Some aspects of the harmonised elections fell short of the requirements of the constitution of Zimbabwe, the Electoral Act and the SADC principles and guidelines governing democratic elections," the head of the team, Nevers Mumba, told a news conference on Friday.

Police sealed off roads around the election results centre on Friday morning, and members of the public were being stopped for questioning, a Reuters reporter in the capital Harare said.

ZANU-PF secretary for finance Patrick Chinamasa told reporters late on Thursday that the ruling party was on course to achieve a two-thirds majority in the National Assembly.

The early results on Friday showed ZANU-PF retaining its rural base, while the CCC captured the urban vote, as has been the case in previous elections.

In the highest-profile loss yet for the ruling party, the electoral commission said on Friday that Finance Minister Mthuli Ncube had lost his parliamentary contest to a CCC challenger.

Results from the presidential election are expected within five days of voting.

ZANU-PF's Chinamasa said the party was "on target" to achieve 60-65% for President Mnangagwa, and dismissed Chamisa's claim that he was leading in the polls as "day-dreaming".

Mnangagwa took over from longtime strongman Robert Mugabe after a 2017 coup and won a disputed election in 2018.