Nelson Mandela, the former SA President returned to his rural home in June after being discharged from hospital [EPA]

South African police on Thursday opened an investigation after two international news agencies set up surveillance cameras outside Nelson Mandela, the former South African President's rural residence.

Police declined to name the media outlets but Britain-based Reuters and US news agency Associated Press both confirmed they had set up cameras outside the ex-president's home in Qunu, in Eastern Cape province.

"Cases against at least two media houses have been opened," police spokesman Vish Naidoo told AFP, adding that they could face criminal charges for violating a law that restricts access to sensitive areas.

Police removed at least two cameras from a house neighbouring Mandela's home on Monday.

South Africa's Times newspaper said the CCTV cameras had been installed possibly six years ago. "We did have a camera and it has been removed," Reuters spokeswoman Joanne Crosby told AFP.

She declined to comment further.

'Not spying'

"The cameras were positioned some time ago, with the knowledge of authorities. The cameras are not turned on. They are not spying on Mr Mandela's home," AP spokesman Paul Colford said in an email to AFP.

"They are part of the preparedness that AP and other large news organisations customarily make in the event of a major news story involving a former world leader."

Anti-apartheid leader Mandela returned to his rural home in June after being discharged from hospital in January for an acute respiratory infection.

The frail 93-year-old's health has sparked intense national and international media attention.

His last public appearance was during the closing ceremony of the 2010 World Cup in Johannesburg, where he was wheeled in and waved joyfully to the crowd.

"So far we've managed to recover two cameras in a house in the village not far from Mr Mandela's house," police spokesman Mzukisi Fatyela told AFP earlier.

"The cameras were put there without the knowledge of his family or the authorities."

Mandela was elected South Africa's first black president in 1994 and served one term before stepping down in 1999.

Source: Agencies