Some of those targeted had previously fled to the South African embassy
Armed militia have raided two camps for people fleeing post-election violence in Zimbabwe, opposition and medical officials have said.
The opposition said several people were killed in Gokwe, north of Harare, but other reports say there was one death.
In Ruwa, near the capital, masked men in army fatigues beat up people who had previously sought refuge at the South African embassy, a witness said.
A BBC correspondent says the raids could threaten moves to share power.
At least eight of those attacked in Ruwa were taken to hospital and about 14 people - mostly from a patrol that camp occupants had organised to maintain security - were missing, the witness said.
About 400 people have been sheltering in local squash courts in Ruwa after being moved on from the South African embassy.
At the G8 summit of the world's leading industrialised countries in Japan, UN Secretary General Ban Ki-moon called on Zimbabwe's political parties to work together to restore the rule of law.
We are saying no party can govern alone in Zimbabwe and therefore the parties have to work together
Tanzanian President Jakaya Kikwete
The US and the UK want the UN Security Council to tighten targeted sanctions against Mr Mugabe and his close allies this week, as well as impose an arms embargo.
But Tanzania's President Jakaya Kikwete, who also heads the African Union, said African leaders favoured some sort of power-sharing government.
The Zimbabwean government blames interference from Western countries for delaying a solution to the country's political impasse.
Justice Minister Patrick Chinamasa said "meddling" by Britain, the US and the European Union was complicating the dialogue between Mr Mugabe's party and the opposition.
The opposition Movement for Democratic Change says 5,000 of its members are missing and more than 100 of its supporters have been murdered since elections in March.
Tens of thousands of people have been displaced.
The MDC accuses the army and ruling party militias of being behind the violence - charges denied by President Robert Mugabe.
The raids came shortly after South African President Thabo Mbeki held talks with Mr Mugabe and members of a breakaway opposition MDC faction over the weekend.
Mr Mbeki is the chief regional negotiator on Zimbabwe, and has been trying to persuade both sides to form a unity government.
There are reports that the South Africans have come up with a proposal that the MDC is prepared to consider, the BBC's Peter Greste reports from Johannesburg.
But it is difficult to see how things can advance, particularly in the light of the most recent attacks, our correspondent says.
Mr Tsvangirai boycotted the talks, saying meeting Mr Mugabe at State House would mean recognising his legitimacy as president.
He has previously said that the violence has to end before there can be any talks on sharing power.
Mr Mugabe has said the opposition must accept him as leader before any negotiations.
At the G8 summit, Tanzania's president alluded to differences between African and Western nations in their approach on Zimbabwe.
Mr Mugabe met one opposition leader (r) but not Morgan Tsvangirai
Mr Kikwete was speaking next to US President George W Bush, who said leaders had discussed Zimbabwe extensively.
"I care deeply about the people of Zimbabwe, I am extremely disappointed in the elections which I labelled a sham election," Mr Bush said.
Mr Kikwete said African countries shared the American president's concerns.
He said: "We are saying no party can govern alone in Zimbabwe and therefore the parties have to work together, come out to work together in a government and then look at the future of their country together."
UK Prime Minister Gordon Brown said pressure for tightened sanctions was growing.
"I don't think anybody is recognising the legitimacy of the regime and it is important that we send a very strong message internationally that this is not acceptable," he said.
A small number of African states has joined the European Union, the US and other Western nations in criticising the way the election was run.
MDC leader Morgan Tsvangirai won the first round of presidential elections in March, but official results gave him less than the 50% needed to avoid a run-off.
Mr Tsvangirai pulled out of the 27 June presidential run-off against President Mugabe, citing the election violence.
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