Nelson Chamisa, who leads the opposition Citizens Coalition for Change (CCC), said political gatherings in four rural areas had to be called off this week after attackers beat up would-be attendees and damaged their vehicles.
"There is unprecedented violence -- terror has become a daily dose," he told a press conference in the capital Harare.
"People in those communities are not allowed to freely associate."
Chamisa, who is on a rural outreach drive in preparation for next year's vote, accused the government of coordinating a campaign of violence against his supporters.
"We have government ministers who are behaving like little thugs... They literally incite violence, coordinate violence and sponsor violence," he said.
A police spokesman said they were "yet to receive any reports" of the alleged violence.
The CCC is an offshoot of the Movement for Democratic Change Alliance party, which lost by a tight margin against the long-ruling ZANU-PF party in Zimbabwe's 2018 general elections.
ZANU-PF representatives could not immediately be reached by phone to comment on Chamisa's allegations.
The Committee to Protect Journalists (CPJ) issued a statement claiming four journalists were also victims of a "brutal assault" after filming a convoy of ZANU-PF vehicles on Thursday that were reported to be blockading the CCC rally in the central town of Gokwe.
"Zimbabwean authorities must investigate and hold those responsible to account," CPJ's Africa coordinator Angela Quintal said in a statement.
They must "ensure that the press can report freely without fear of attack, especially with the country set to hold national elections next year", she said.
The CCC, formed in January this year, won two-thirds of seats up for grabs in parliamentary and municipal by-elections in March.
This raised hopes in the party that it could secure nationwide victory in general elections, likely to be held in the first half of 2023.
There is rising discontent in Zimbabwe as President Emmerson Mnangagwa, who replaced long-time ruler Robert Mugabe in 2017, struggles to ease entrenched poverty, end the country's chronic power cuts, and rein in inflation -- which reached more than 280 percent in August.
Rights groups have complained of repeated arbitrary detentions and often exceptionally harsh custody under Mnangagwa.
The former British colony has been ruled by the ZANU-PF since independence in 1980, except between 2009 and 2013 when Mugabe was forced into a power-sharing government with veteran opposition leader Morgan Tsvangirai following disputed elections.