ZANU-PF and the police yesterday condemned the interference by the United States in investigations into the murder of an MDC-T activist in Mudzi.
The US Embassy in Harare released a statement yesterday accusing Zanu-PF of committing the offence.
It also accused the police of failing to take action to stop the murder of the MDC-T supporter.
But police say they are still investigating the murder of Cephas Magura and so far six suspects have been arrested.
The US Embassy said in the statement: "The United States condemns the murder of Cephas Magura by Zanu-PF supporters in Mudzi during a May 26 MDC-T rally.
"We are deeply concerned by reports that the Zimbabwe Republic Police on the scene refused to uphold the law or protect the public by failing to stop Zanu-PF supporters from violently attacking lawfully-assembled MDC-T supporters."
The embassy said the US condemns Zanu-PF activists "responsible for committing these attacks and the members of the Zimbabwe Republic Police who failed to fulfil their official duty to serve and protect their fellow Zimbabweans".
"We call on the Zimbabwe Republic Police and the Zanu-PF disciplinary committee to conduct a thorough investigation of these events on May 26 and to uphold all responsible for this atrocity to account," the embassy said.
But Zanu-PF and the police equated the remarks to interference in the country's internal affairs.
"We are condemning in the strongest terms the interference by the US embassy in the internal affairs of Zimbabwe," said Zanu-PF spokesperson Cde Rugare Gumbo.
"Americans claim they are a democratic country and they recognise the rule of law as such they should allow due process to take place."
Cde Gumbo said the incident surrounding the death of the MDC-T activist now appears rehearsed to coincide with the Sadc extraordinary summit in Angola.
"The incident was meant for the Sadc extraordinary summit in Angola," he said.
"The whole exercise is also meant to damage the image of Zanu-PF with the MDC-T provoking the situation to attract attention."
Police took a swipe at the US embassy with Assistant Commissioner Wayne Bvudzijena expressing surprise at the remarks by the Americans.
"We are surprised by their (US embassy) action," he said. "We do not need anyone to call upon us to do our duty. The Constitution clearly states what our responsibilities are.
"We are also surprised how they have reached at their conclusion when the police are on the ground investigating the murder."
Asst Com Bvudzijena added: "They (US Embassy) can shout as much as they want. We are doing what we are doing because we have to do that as the police."
He said the suspects will be sent to court for prosecution once police gather enough evidence.
Asst Comm Bvudzijena said at the moment they were waiting for post mortem results to conclude investigations.