Zimbabwe's opposition leader on Wednesday accused the ruling ZANU-PF government of plunging the country into crisis by "rigging" a tense election marred by long delays and reports of voter intimidation.

"This is a clear case of voter suppression, a classic case of Stone Age, antiquated, analog rigging," Nelson Chamisa, 45, the head of the leading opposition party, the Citizens Coalition for Change (CCC) told a press conference in the capital.

Less than a quarter of polling stations in Harare opened on time, according to electoral authorities, which blamed the problem on delays in the printing of ballot papers.

Voting at one polling station in Harare's Warren Park suburb, only opened 12 hours late -- the same hour the polls were scheduled to close, an AFP reporter said.

Chamisa blamed the governing ZANU-PF party, which has ruled the country since independence in 1980, for the delays, saying it said was "desperate" to cling to power.

President Emmerson Mnangagwa, 80, who came to office after a coup that deposed late ruler Robert Mugabe in 2017, is seeking a second term in an election that came to a backdrop of widespread discontent at the southern African country's economic troubles.

Ballots at a polling station in Kambuzuma township on the outskirts of Harare, arrived only after 2:30 pm (1230 GMT) whereas polling had been scheduled to start at seven am.

"I am very frustrated and disappointed," said Linda Phiri, 53, an angry mother of three, who had been queuing since six am.

"But I am going to sleep here, I am not going home... I want to cast my vote, my children are suffering with no employment, no education, we cannot afford it."

Tipi Mvere, an 81-year-old man with a white beard who stood at the front of the queue with the help of a walking stick, said he also had been waiting more than eight hours to vote.

"My vote is my right," he said, explaining his determination to stay.

The poll is being watched across southern Africa as a test of support for the ZANU-PF party, whose 43-year rule has been battered by an economic slump and charges of authoritarianism.

The opposition has been hoping to ride a wave of discontent over corruption, high inflation, unemployment and entrenched poverty.

Chamisa also alleged voters have been "terrorised" in rural areas, where rights groups said an organisation linked to the ruling party intimidated voters.

Voters queue outside a polling station during Zimbabwe's presidential and legislative elections in Harare
Voters queue outside a polling station during Zimbabwe's presidential and legislative elections in Harare AFP
A monitor from the EU Election Observation Mission looks at a voters' list at a polling station during Zimbabwe's elections in Kwekwe
A monitor from the EU Election Observation Mission looks at a voters' list at a polling station during Zimbabwe's elections in Kwekwe AFP