The US embassy has warned its citizens to avoid areas where demonstrations are likely ahead of a large protest planned by Zimbabwe opposition parties for Harare on Friday.
In a security message released on Thursday, the embassy said it was likely that riot police would "increase their numbers through [Friday] morning in anticipation of this event."
"Even demonstrations intended to be peaceful can turn confrontational and escalate into violence," the embassy said in a nod to ugly clashes with riot police that broke out during a march by youths from the main opposition Movement for Democratic Change on Wednesday.
Discontent is rising in Zimbabwe on the back of high unemployment, cash shortages and brutality from a police force that appears overwhelmingly loyal to President Robert Mugabe and his party. Protests have been taking place with mounting frequency in the last few weeks - and there are claims that innocent bystanders have been targeted by riot police.
It has been reported that tear-gas is also being liberally used by the police force.
Officials from some of the 18 parties billed to take part in Friday's demonstration have vowed it will go ahead even though police have said it shouldn't.
The High Court is due to rule on the matter Friday in a hearing due to start at 8am - exactly when marchers have been told to gather.
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