Harare: Four opposition party activists were killed overnight and three homes were firebombed, the main Zimbabwe opposition party said on Thursday, evidence that violence was escalating even as South African President Thabo Mbeki tried to mediate the conflict.

The spokesman for the Movement for Democratic Change (MDC), Nelson Chamisa, said the four were abducted in the township of Chitungwiza, 25 kilometres south of the capital and were assaulted with iron bars, clubs and guns.

Shots were fired, leaving cartridge cases where the bodies were found early yesterday, he said.

Witnesses said the victims were forced onto trucks and taken away by militias chanting slogans of President Robert Mugabe's party.

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

The opposition has said more than 60 of its activists have been killed in recent weeks. The party has accused Mugabe of unleashing violence to ensure a victory over opposition candidate Morgan Tsvangirai in a presidential run-off election next week.

Independent human rights activists have implicated police, soldiers and Mugabe party militants in the violence.

Chamisa said militants linked to Mugabe's party and army troops patrolled Chitungwiza for days, visiting houses at night and threatening occupants.

Doctors at Parirenyatwa hospital in Harare said yesterday they admitted victims injured in assaults in the townships of Mbare, Mabvuku and Tafara on the outskirts of Harare in recent days as political violence spread from rural areas to the city.

Residents of Harare's well-to-do suburbs of Chisipite and Newlands reported gangs of militants forcing household workers and family members to attend meetings known as "pungwes" - night-long political indoctrinations used by militants since the independence war swept Mugabe to power in 1980.