Seven Chinese nationals who smuggled Malawians to South Africa and subjected them to forced labour have been handed 20-year prison terms each.

The four men and three women were found guilty of human trafficking and kidnapping earlier this year by a South African court.

Their sentence comes nearly six years after they were arrested when local authorities raided a factory in Johannesburg and found 91 Malawian nationals, 37 of them children, working in appalling conditions.

Human trafficking is a major concern in South Africa, with the country regarded as a "source, transit and destination", according to the government.

The group - Kevin Tsao, Chen Hui, Qin Li, Jiaqing Zhou, Ma Biao, Dai Junying, and Zhang Zhilian - were found guilty on 158 of the 160 counts for which they were charged.