The High Court of Zimbabwe has acquitted six opposition party activists whom President Robert Mugabe had labeled terrorists for their alleged role in the murder of a ruling party ally in 2001.

The decision, handed down Thursday, ended one of Zimbabwe's most politically charged court cases. Among those exonerated were three men -- Remember Moyo, Sazini Mpofu and Khethani Augustine Sibanda -- who were held without bail for two years and, they said, repeatedly tortured into making false confessions.

Justice Sandra Mungwira issued the ruling before the defense had presented its case. In March, Mungwira chastised police officials for not being truthful and ruled that the confessions and police testimony were so tainted as to be inadmissible. Mungwira also held open the possibility that, as the defense claimed, government agents -- whom she called a "third force" -- may have controlled the investigation.

The body of the victim, Cain Nkala, was found in a shallow grave outside the city of Bulawayo in November 2001. Nkala, who was the leader of an association of war veterans in the city, had been strangled. Police blamed the murder on the main opposition party, the Movement for Democratic Change, and at one point detained more than a dozen party activists in connection with the case.

At Nkala's funeral, Mugabe said: "The MDC and their supporters should know their days are numbered. . . . The time is now up for the MDC terrorists, as the world has been awakened by the death of Nkala."

The opposition party contended throughout the case that senior officials in Mugabe's party, the Zimbabwe African National Union-Patriotic Front, had ordered Nkala's killing.

"ZANU has a long history of killing its own," said David Coltart, an opposition member of parliament from Bulawayo. "I think that Cain Nkala's killing is potentially just part of this long line."

The motive, Coltart said, was to cover up an earlier killing of an opposition party activist, Patrick Nabanyama. Nkala had been implicated in that killing and, in the days before his death, was reportedly preparing to reveal that top members of Mugabe's party were also involved. Both murders remain unsolved.

Mugabe has ruled Zimbabwe since the country gained independence in 1980. Over the past four years, he has used increasingly authoritarian means of tightening his control over speech, the news media, political debate and aid groups, according to international human rights organizations.

President Robert Mugabe's ruling party has been accused of ordering a former ally killed.