Dozens of people, including an opposition MP, were injured and property damaged in south-west Zimbabwe following violent clashes between political parties on Monday.
They were allegedly attacked as they campaigned ahead of by-elections this coming weekend.
Thirty people sought medical treatment for a various injuries, a local human rights group told the BBC.
Increasing numbers of incidents of political violence have raised concerns as Zimbabwe prepares for general elections next year.
The group from the opposition party Citizens Coalition for Change say the Monday attack was carried out by ruling party members.
The same group was attacked over the weekend with some pictures showing some women in the group were stripped off their clothes.
Police say they received complaints from both parties and are investigating.
Human rights lawyers have decried the levels of violence against the opposition in recent months.
