The US ambassador to Zimbabwe on Thursday said opposition supporters had been murdered, abducted and forced from their homes in a spate of violence in rural areas since last month's elections.
"There is growing evidence that rural communities are being punished for their support for opposition candidates," Ambassador James McGee said in a message to Zimbabweans delivered on the eve of independence day.
"We have disturbing and confirmed reports of threats, beatings, abductions, burning of homes and even murder, from many parts of the country."
McGee, whose government has been one of the leading critics of Zimbabwean President Robert Mugabe, is the first ambassador to back claims by the Movement for Democratic Change (MDC) that its supporters are being targeted.
The MDC says two of its supporters have been killed by followers of Mugabe's ZANU-PF. The police have only confirmed one of the killings, and say the motive has yet to be established.
A coalition of Zimbabwean doctors says its members have seen and treated more than 150 patients who had been beaten and tortured since the elections.
McGee said an atmosphere of fear meant that many Zimbabweans were unable to celebrate their independence from Britain.
"Independence days provide a chance to reflect on proud achievements, a united sense of purpose and the future," he said.
"Sadly, as Zimbabwe celebrates its 28th birthday, many Zimbabweans are unable to celebrate. What should be a proud and joyful day for Zimbabweans is overshadowed by uncertainty and fear."
