South African police must investigate 'Zimbabwe torture'
South Africa's Supreme Court of Appeal has upheld an order for police to investigate Zimbabwean officials over allegations they tortured opposition figures in 2007.
Under international law, South Africa had a duty to investigate crimes against humanity, the judge said.
The police and prosecutors had refused to investigate the officials, saying it was not in their jurisdiction.
Correspondents say the ruling is likely to strain relations with Zimbabwe.
The Southern Africa Litigation Centre (SALC) and the Zimbabwe Exiles Forum (ZEF) filed the case to force South Africa to arrest and prosecute 17 Zimbabweans accused of torture in 2007 if they entered the country.
'Assault on sovereignty'
Police "are required to initiate an investigation... into the alleged offences," Judge Mohammed Navsa said in his ruling.
SALC welcomed the ruling.
"The Supreme Court ruling confirms that the dispensing of international justice is not restricted to international forums, and commits the South African authorities to play their part in ensuring that torturers and other international criminals are held accountable for their actions," its deputy director, Priti Patel, said in a statement.
South Africa's National Prosecuting Authority (NPA) spokesperson Nathi Ncube also welcomed the judge's ruling.
According to Mr Ncube, the ruling makes it clear that the police should be the ones carrying out any investigations.
"Our duty is to prosecute cases, the police's duties is to investigate. From where we are sitting, this ruling does not affect the NPA," he told the BBC.
When the case was first heard, Zimbabwe's President Robert Mugabe described the court action as an "assault of Zimbabwe's sovereignty" and petitioned the South Africa's governing African National Congress (ANC) party to intervene.
But Judge Navsa found that as a country that recognised the International Criminal Court, South Africa was obliged to investigate reports of human rights abuses.
The case centres on an incident in 2007, when supporters of the opposition Movement for Democratic Change say they were tortured after a raid on their party headquarters in Harare.
In 2008, SALC says it submitted a dossier to the NPA containing "evidence" of the involvement of Zimbabwean officials in the alleged perpetration of crimes against humanity.
The docket is alleged to include evidence of excessive torture and beatings including the use of baseball bats, water-boarding and electrical shocks allegedly being applied to genitalia by Zimbabwean officials.
During his ruling Judge Navsa cited the dossier, which is about 50 pages when redacted - and said it warranted further investigation.