The main opposition party has urged Zimbabweans to "rise up in their millions" against President Robert Mugabe next week.
Tsvangirai warns his supporters to be ready for trouble
The Movement for Democratic Change (MDC) has called a week-long strike so people can take part in prayer meetings and "democracy marches".
The MDC accuses Mr Mugabe of rigging elections last year and using state security agents to persecute his opponents.
The government, the army and pro-Mugabe militias have all said they will crush any protests.
In a statement published in the state-run Herald newspaper on Thursday, the army said it would "bring to bear its full force upon those perpetrators of uncalled for violence".
We are ready to crush any demonstrations which will lead to the destruction of property or is a threat to national security
Kembo Mohadi, home affairs minister
MDC spokesman Paul Themba Nyathi said the protests would not stop until "Mr Mugabe gives a clear signal that he will leave office".
This is the first time the MDC will engage in mass action against the government.
The MDC leadership has been criticised by some of its activists for not doing more to make life difficult for Mr Mugabe.
Analysts say Zimbabwe's economy is on the brink of collapse - the latest evidence being a shortage of bank notes.
Last week, there were long queues outside banks despite limits on cash withdrawals.
There have been shortages of basic commodities such as bread, sugar and petrol for several months.
Zimbabweans are getting used to queues
The latest statistics show annual inflation is running at 269%.
Some eight million people require food aid, according to aid agencies.
The opposition blame the shortages on economic mismanagement, while Mr Mugabe says they are a result of a Western plot to bring him down.
As the pressure on Mr Mugabe's Government has increased, so-called "war veterans" loyal to his Zanu-PF Party have threatened to use force to prevent any opposition protests.
"Using our military experience, we will mobilise," warned Patrick Nyaruwata, chairman of the Zimbabwe National Liberation War Veterans' Association.
"We are ready to crush any demonstrations which will lead to the destruction of property or is a threat to national security," Home Affairs Minister Kembo Mohadi said earlier this week.
But MDC leader Morgan Tsvangirai told thousands of supporters that he was not afraid.
"We must be prepared to be arrested, we must be prepared to make a mark to ensure that we will never again be oppressed," he said.
The main trade union umbrella organisation has urged workers to stock up on the staple food, maize-meal, and cash ahead of the mass protests.