Campaigning has been relatively peaceful across the country
Zimbabwe's security forces have been put on full alert ahead of Saturday's general elections, amid opposition fears of poll-rigging.
Tanks have been patrolling the streets of the capital, Harare. Armed soldiers have been deployed in other towns.
President Robert Mugabe is facing his strongest challenge since he gained power at independence in 1980, with two other candidates in the running.
Mr Mugabe insists the vote is fair and everyone should abide by the results.
The chiefs of Zimbabwe's police, army, prison service and intelligence services gathered in Harare to warn that violence would not be tolerated.
Augustine Chihuri, commissioner general of the police, said: "The defence and security forces of Zimbabwe are on full alert from now onwards covering the election period and beyond."
He said they would "thwart all threats to national security".
Mr Chihuri also said candidates would not be allowed to declare victory before official results were announced.
On Thursday, Mr Mugabe warned opponents not to protest if they lost. "Just dare try it," he said at one of his final rallies.
Mr Mugabe and wife Grace push for votes in Harare
A BBC contributor in Masvingo in south-eastern Zimbabwe says there is an increased military presence and fly-pasts by Chinese-made fighter jets.
One 54-year-old villager told him: "We have been warned that if we vote Mugabe out, there will be war."
Another Masvingo resident said he would not be cowed by intimidation: "We do not mind even if they deploy soldiers at polling stations - it's time for Mugabe to go."
Some 100 soldiers armed with assault rifles are also patrolling in the eastern city of Mutare.
In his final campaign rally, Mr Mugabe, 84, repeated his accusation that the opposition were Western puppets.
"This is a vote against the British. The fight is not against the MDC [Movement for Democratic Change]... the MDC is just a puppet, a mouthpiece of the British," he told 6,000 people on the outskirts of Harare, according to Reuters news agency.
OPPOSITION POLL CONCERNS
Surplus ballot papers printed
Tens of thousands of "ghost voters"
Police allowed inside polling stations
More polling stations in rural areas
State media bias
Food aid only given to Zanu-PF supporters
Chiefs used to campaign for Zanu-PF
The MDC denies these charges and says it is fighting to save Zimbabwe's economy.
The country has the world's highest inflation rate at more than 100,000% and just one adult in five are believed to have regular jobs.
Former Finance Minister Simba Makoni, who is running as an independent candidate, said repairing the economy could take "10 to 15 years".
MDC leader Morgan Tsvangirai and Mr Makoni are Mr Mugabe's strongest challengers.
On Thursday they issued a joint statement expressing severe concerns about the poll.
They said they had still not received full nationwide voters' lists that could be verified, and suspected there were many thousands of "ghost voters".
The MDC says that in Hatcliffe, just north of Harare, some 8,000 people had been registered to vote in a small area where there are only 36 houses.
HAVE YOUR SAY
It's a country without hope with a dictator who will stop at nothing to remain in power.
Barry Verona, Ex pat - now Canada
The BBC's Southern Africa correspondent, Peter Biles, says one major worry is that there may not be enough polling stations in urban areas.
He says there is also concern about equal access to the media.
The government has accused Britain and the US of already having decided that the elections will not be free and fair.
However, campaigning has been relatively peaceful, with none of the widespread intimidation of opposition activists seen in polls in recent years.
Both Mr Makoni and Mr Tsvangirai have been able to hold rallies across the country.
A total of 5.9 million people are eligible to vote in Saturday's joint local, senate, assembly and presidential polls.
A candidate must win more than 50% of the presidential vote to avoid a run-off in three weeks' time.
But Mr Mugabe says land and control of economic resources are the main issues.
He blames the UK and the US want to remove him from power to reverse his seizure of white-owned land.
If you are voting on Saturday send us your experiences by text on +44 7786 20 50 85.