Zimbabwe's main opposition group has said it will hold anti-government protests in the capital Harare, in defiance of a police ban.
The opposition Movement for Democratic Change (MDC) has called for mass protests against the government's handling of the economy.
About five million Zimbabweans are in need of food aid, according to the UN.
The MDC has said it has given the authorities assurances the protests will be peaceful.
But police say they have evidence the protests will be violent.
The BBC's Shingai Nyoka in Harare says there is a heavy police presence, but no protesters, in Africa Unity Square where the march was due to begin at 09:00 local time (07:00 GMT).
The MDC's headquarters are also surrounded by security forces and the city centre is subdued, with most shops closed, she adds.
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A "prohibition notice" banning the demonstrations has been issued by authorities in Harare's central district, police spokesman Paul Nyathi said.
"The police will be conducting patrols, surveillance, stop-and-searches to ensure law and order is maintained in all areas of the country," he added.
In response, an MDC official told Reuters news agency that the party was not aware of the prohibition order and the demonstrations would take place as planned.
The official said, given the party had complied with law by notifying police of the protests, it expected them to "ensure there is peace".
Life 'worse than under Mugabe'
The protests were called to protest at Zimbabwe's worsening economic situation, which has seen power cuts of up to 18 hours a day, rising inflation and the return of the Zimbabwe dollar.
"Life in Zimbabwe today is worse that it was under Robert Mugabe," MDC politician Fadzayi Mahere told the BBC.
"People are marching against the continued hardship that they face. The cost of living has soared exponentially, we're back into hyperinflation."
She said that democratic freedoms were also under threat.
Earlier this week, at least six civil society and opposition members were allegedly abducted and tortured.
The Zimbabwe Human Rights NGO Forum says the victims were accused of mobilising people to demonstrate.
Human rights groups blame state agents for their disappearance, but the authorities have denied their involvement.
The UK and US have expressed concerns about the reports.
What's the background?
If the protests do go ahead, they will be the first since rallies against fuel price increases in January led to deadly clashes with troops, killing 12 people.
In recent months, Zimbabwe's economy has deteriorated, feeding into wider grievances with the ruling Zanu-PF party under President Emmerson Mnangagwa.
Mr Mnangagwa swept to power in November 2017 after long-time leader Robert Mugabe was ousted in a military coup.
Mr Mnangagwa, a long-time ally of Mr Mugabe, called elections, held the following year on 30 July, which he won. On the campaign trail, he promised democratic reforms and economic recovery after years of decline under Mr Mugabe.
But the mood of hope and change in the wake of Mr Mugabe's removal from power has diminished as Zimbabwe's economy has faltered.
Inflation is at a 10-year high, shrinking Zimbabweans' salaries and pensions. Shortages of fuel, power and water are widespread and the price of bread has increased five-fold since April.
Opposition groups feel that the president is failing to live up to his promises following his election in disputed polls.
There are fears, however, that protests in Harare and other major cities will lead to another police crackdown akin to January's.