Renewed violence has ended hopes of negotiating an end to Zimbabwe's political crisis, the country's main opposition party has said.
The Movement for Democratic Change (MDC) blamed President Robert Mugabe's Zanu-PF party for an "orgy of brutality" across Zimbabwe.
The statement came ahead of regional talks in South Africa this weekend on Zimbabwe's political stalemate.
South Africa's government has said it will take a tough stance at the summit.
Mr Mugabe and MDC leader Morgan Tsvangirai signed a deal to share power in September, following disputed elections and widespread violence earlier this year.
But the two sides have not been able to agree on how to share cabinet posts.
On Thursday, the MDC said Mr Mugabe's party had "unleashed a new orgy of brutality and assaults across the whole country".
"In short, Zanu-PF killed the dialogue despite the hopes, patience and expectations of the people of Zimbabwe," it said in a statement.
MDC spokesman Nelson Chamisa told the AFP news agency that Morgan Tsvangirai would still attend Sunday's summit of the Southern African Development Community (Sadc), but that the recent violence had shown Mr Mugabe's lack of sincerity.
An earlier MDC statement said a Zanu-PF militia group had attacked at least 25 MDC supporters in the capital, Harare, last week.
Three days later, state security forces had raided homes belonging to MDC supporters and arrested nine people, including a two-year-old child, it added.
There has been no immediate comment from the Zimbabwean authorities on the allegations.
The Sadc summit this weekend comes after recent talks failed to break Zimbabwe's deadlock.
Mr Tsvangirai's MDC says President Mugabe and his party, Zanu-PF, are trying to grab all the most important ministries.
The key sticking point at the latest round of talks was control of the home affairs ministry, which is responsible for the police.
A spokesman for the South African government, Themba Maseko, said the host country wanted to ensure a deal was reached.
"The failure of the parties to agree is something that is becoming a major political hindrance to the stability that we desire," he said.
"It's government's view that the heads of state must now take urgent steps to make sure political solutions are found," Mr Maseko said, according to AFP.
President Mugabe's government has published a gazette, giving the ministries of defence to justice Zanu-PF. But he has reportedly agreed to let the MDC have the finance portfolio.
Under the deal, Mr Tsvangirai would become prime minister in the new government, tasked with ending the country's economic crisis.
Zimbabwe is facing severe food shortages and rampant inflation.
Sunday's summit is also expected to discuss recent fighting in the Democratic Republic of Congo.