A posse of South African farmers and army reservists tracked down a gang of armed robbers in a rural manhunt and shot three of the eight criminals dead, police said Thursday.

Civil rights activists expressed alarm that the killings could be part of a growing trend for citizens, sick of violent crime and the state's apparent inability to combat it, to take the law into their own hands and might also raise racial tensions.

The mainly white 100-strong band assembled hastily after an elderly farmer and his wife raised the alarm during an attack on their farm in the cattle-raising and maize-growing northwest.

"Police arrived later and joined the search in the direction of the fugitives and discovered three people who were dead. They were members of the gang," police spokesman Louis Jacobs said.

Each had been shot.

The five other black gang members, all from the Johannesburg area that is the country's worst crime spot, were arrested, two of them with gunshot wounds.

Army reserve units, or commandos, are dotted across rural South Africa. Jacobs said it was unclear if the reservists, often farmers themselves, had acted as a unit or unofficially.

He said it could take a month before police could say if the robbers had been shot in a battle or killed execution-style.

"If there was a gun battle, that would make it more understandable but still a disturbing indictment on our society, which must be one of the most violent on earth," violence monitor Mary de Haas told Reuters.

She said rough justice had been around for a long time in a country where blacks had never had much faith in the police and where whites had also now lost theirs.

"Public opinion would say that if these people attacked an elderly couple, why not shoot them dead anyway even if they put up no opposition," she said.

Groups bearing the brunt of a post-apartheid crime wave, from isolated white farmers to the defenseless township poor, have increasingly been taking the law into their own hands.

Farms, far from neighbors and assistance, have made easy targets for robbers. The Human Rights Commission says some 500 farmers have been murdered since the end of apartheid in 1994.

The commission said they were witnessing a backlash in attacks by farmers on defenseless blacks.