The official election results released at the beginning of May had Tsvangirai edging out President Robert Mugabe in the election. However, according to that disputed tally, he failed to win more than 50 percent of the vote so a run-off has been scheduled for June 27.
Tsvangirai's party, the Movement for Democratic Change, claims Mugabe's party is using violence and intimidation against opposition supporters, especially in rural areas, to affect the outcome of the next round of voting.
"I've been saddened that Zimbabweans are willing to shed the blood of other Zimbabweans over political differences," Tsvangirai told a news conference in the capital Harare.
"We are proceeding to compile the names of those who've committed these crimes. We will approach the attorney general to do something about it."
MDC chief spokesman Nelson Chamisa told Agence France-Presse that supporters have been displaced in rural areas and "key players have been abducted and killed rendering our campaign crippled."
In comments made earlier this month, Mugabe accused the MDC of being behind the political violence, despite reports by United Nations representatives saying the violence was primary directed at MDC supporters.
"We have disturbing evidence of motorized gangs trained and equipped by the MDC and of returning white commercial farmers who have been visiting terror on villages and party supporters," said Mugabe, according the Herald, a Zimbabwe paper.
The U.S. ambassador to Zimbabwe, James McGee, traveled outside of Zimbabwe's capital in May and observed both victims of violence and displaced people who would be unable to vote in a run-off because they aren't living in the wards where they are registered.
"We're talking about large numbers of people who are being intimidated by violence," McGee said.
"We saw images, horrible images, of people who had been beaten senseless, again for nothing more than voting their conscience in the last election."
Zimbabwe's police Chief Augustine Chihuri said Tuesday the force had a duty to defend the country from what he called a threat from foreign powers and their local puppets, a term Mugabe has used often to describe the MDC's relationship with Britain.
The 84-year-old president has been in power for nearly 30 years, and has blamed his poor showing in the March election on divisions within his party. The initial election results were delayed by more than a month, and the MDC accused Mugabe of buying time to orchestrate a way to reclaim power.
Tsvangarai has called for increased presence of international election observers for the run-off, and the Southern African Community, SADC, has agreed to send additional monitors above the 120 provided in March.
