"Twenty-one people have been killed in a road accident," Spot FM radio reported, saying the accident occurred near the southeastern town of Chisumbanje.
A large number of victims were thought to be travelling in a truck which sideswiped an ethanol tanker.
"Most of the dead were burnt beyond recognition. Charred bodies were scattered on the road while others are still trapped under the wreckage of the haulage truck," the radio said.
Police spokeswoman Charity Charamba confirmed the accident but could not give the exact number of victims.
Road accidents are common in Zimbabwe, where highways are riddled with potholes due to years of neglect.