Four opposition party activists were killed and three homes firebombed near the capital as militants linked to the ruling party and army continued a campaign of intimidation ahead of a runoff election, the opposition said Thursday.

The activists were abducted Wednesday in the township of Chitungwiza, 15 miles south of the capital, and were assaulted with iron bars, clubs and guns, said Nelson Chamisa, spokesman for the Movement for Democratic Change.

The victims were forced onto trucks and taken away by militias chanting slogans of Mugabe's party, witnesses said. The bodies were found early Thursday, he said.

In a separate incident, three Chitungwiza opposition councilmen and their families fled their homes and escaped injury when their homes were set alight by gasoline bombs Wednesday night, he said.

Attempts to reach Zimbabwean police for confirmation of the firebombing were not immediately successful.

Chamisa said militants linked to Mugabe's party and army troops patrolled the township for several days, visiting houses at night and threatening occupants. The opposition says more than 60 of its activists have been killed in recent weeks.

Independent human rights activists have implicated police, soldiers and Mugabe party militants in the violence, thought to be aimed at ensuring victory over opposition candidate Morgan Tsvangirai.

Doctors at the main Parirenyatwa hospital in Harare said Thursday they admitted victims injured in assaults in several townships on the outskirts of Harare in recent days as political violence that has plagued rural areas spread to the city.

Residents of Harare's well-to-do suburbs reported gangs of militants forcing household domestic workers and family members to attend meetings known as a "pungwe," a colloquial term for night-long political indoctrination used by militants since the independence war that swept Mugabe to power in 1980.

Mugabe has threatened to return the country to war if he does not win the runoff June 27.

"They came and dragged my workers to the vlei," overgrown grassland nearby, Oliver Mberi said. "You'd think we are already at war." He said neighbors reported employees living in the dormitory townships fleeing violence in townships seen as opposition strongholds.

On Monday night, Abigail Chiroto, the wife of MDC mayor elect of Harare, was seized from her house in the suburb of Hatcliffe with her four-year-old son Ashley, family friends said Thursday. The friends, who did not want to be identified for fear of repercussions, said the two were taken to a nearby farming area where Chiroto's body was found Tuesday.

The boy, who was left at a nearby police station, told family members that he saw his mother being blindfolded and taken off into the bush. When Chiroto's body was found, she was still wearing a blindfold. Her body was identified Wednesday by her husband Emmanuel who was out of town at the time.

Mugabe "is behaving like a warlord," opposition party spokesman Nqobizitha Mlilo said. "This violence must stop."

The opposition claims Tsvangirai won the country's presidential elections, but official results said a runoff, to be held in just over a week, was needed because there was no outright majority win.

South African President Thabo Mbeki held talks with Tsvangirai on Wednesday and later with Mugabe amid increasing international concern that the June 27 runoff will not be free and fair.

Mbeki, who has steadfastly refused to publicly rebuke Mugabe, left late Wednesday without speaking to reporters. On Thursday, he canceled a press conference with Ethiopian Prime Minister Meles Zenawi "due to unforeseen circumstances," the foreign affairs department said in a statement.

Mbeki's spokesman Mukoni Ratshitanga said he had no comment on Wednesday's meetings in Harare because they were not conducting the negotiations in the media.

Mugabe spokesman George Charamba was quoted in Thursday's edition of the state newspaper The Herald as saying Mbeki came merely to review election preparations.

Mbeki says confrontation with Mugabe could backfire. But Mbeki's decision to spend his 66th birthday with the 84-year-old Zimbabwean autocrat underlined the immense pressure he is under at home and abroad. Mbeki is being urged to take a tougher stance or show that his quiet tactics can work to persuade Mugabe to stop the violence before the election.

Tsvangirai has called on Mbeki to step down as mediator, accusing him of bias toward Mugabe.

Mlilo expressed little confidence that Mbeki's visit would make a difference, noting "four people died that very day" the South African visited.

"Mugabe doesn't seem to care what the international community thinks," Mlilo said.

U.S. Secretary of State Condoleezza Rice demanded action Wednesday.

"It is time for leaders of Africa to say to President Mugabe that the people of Zimbabwe deserve a free and fair election," she said after a meeting in Washington with Kenyan Prime Minister Raila Odinga — one of the few African leaders who has criticized Mugabe.

"You cannot intimidate opponents, you cannot put opponents in jail, you cannot threaten them with jail on charges of treason and expect to be respected in the international community," Rice said.

Most observers praised the conduct of the first round — although not the delay in releasing official results. But there are growing fears that Mugabe will steal the second round through violence and ballot rigging.

In addition to the violence, Tsvangirai's party has seen rallies banned and campaign stops blocked by police, and its No. 2, Tendai Biti, has been arrested on charges of treason. The opposition says the charges are politically motivated.

On Thursday, police presented their case for charging Biti with treason — which can carry the death penalty — and other offenses, including publishing false statements. Formal charges were expected to be filed later Thursday.

The false statement charge was related to Biti's announcement that Tsvangirai won the first round of presidential voting March 29 before official results were released. The opposition claims Tsvangirai won outright, but according to official results, he came first but not with the 50 percent plus one vote needed to avoid a runoff.

Tsvangirai, who attended Biti's hearing, told reporters during a break that he objected to "the manner in which this whole case is being handled.

"It's all part of harassment," Tsvangirai added, saying time spent in court was time away from campaigning.