Zimbabwean riot police fired tear gas and beat opposition supporters on Wednesday after barring a planned address by the main opposition leader, Nelson Chamisa, AFP journalists said.
Hundreds of supporters had gathered outside the headquarters in Harare of the Movement for Democratic Change (MDC) after the party was denied permission to hold a rally in the city's Africa Unity Square.
Chamisa had been expected to make the address from the office balcony instead.
As the crowd danced to party songs blaring from speakers on the balcony, baton-wielding police arrived to disperse them.
An AFP correspondent saw a man with a bleeding gash on the head and a swollen arm after being hit with a truncheon as he left a food outlet.
Several shops and banks yanked down their shutters.
"Many people were beaten up and injured," MDC spokesman Daniel Molokele told AFP. "We condemn the police brutality in the strongest terms".
He said Emmerson Mnangagwa's government was as oppressive as the regime of the man he had ousted, former president Robert Mugabe.
"It's the same old regime. Worse than Smith," he said referring to Ian Smith, the white-minority prime minister of the 1960s and 70s, who declared independence in defiance of Britain, the country's colonial power.
"Maybe they are afraid that what they did to Mugabe in November 2017 will repeat itself," said a man wearing a red MDC beret who identified himself as Terry T, referring to the military-led coup against Mugabe two years ago.
Chamisa had been expected to speak about the general state of the country including its entrenched economic crisis, corruption and crumbling health system.
Zimbabwe's economy, crippled by decades of mismanagement under Mugabe, has failed to rebound under Mnangagwa, and many Zimbabweans say the situation has got worse.
Hyperinflation is wiping out savings; unemployment is estimated at around 90 percent; fuel, medicine and other essentials are in short supply; and doctors and some public-sector workers have stopped going to work as they cannot afford the cost of commuting.
Many families live on one meal a day.
Riot police blocked off a nearby street as a crowd gathered for an address by opposition leader Nelson Chamisa