The latest deaths come before incumbent Robert Mugabe, who leads Zanu-PF, faces Morgan Tsvangirai, who heads the MDC, in a decisive second-round presidential vote.
Zanu-PF lost its parliamentary majority for the first time since 1980 in the first round of voting.
Mugabe has said that his supporters are ready to fight should he lose the vote on June 27 and there have been signs of a crackdown against the MDC.
Zimbabwean police arrested on Wednesday an opposition politician and added six others to a wanted list, state media said on Thursday.
Shuwa Mudiwa, who won his seat for the MDC in March, was arrested for the alleged abduction of a 13-year-old girl, the Herald newspaper reported.
"He was arrested this afternoon in Harare and is still in custody. He will appear in court soon," Wayne Bvudzijena, a police spokesman, told the newspaper.
The six other politicians are wanted on accusations of murder, public violence and malicious damage to property.
The MDC has accused Zanu-PF of leading a campaign of intimidation against opposition supporters in an attempt to influence the vote for Mugabe's benefit.
Tendai Biti, a senior MDC leader, is being held in prison on charges of treason and Tsvangirai has been detained five times while campaigning.
The UN has said that the Mugabe's supporters were to blame for most of the pre-election violence, while Mugabe says the opposition is responsible for the incidents.