The South African government says it is investigating allegations, posted on a website, that the state ombudsman and opposition figures spied for the U.S.

The site, which is titled Africa Intelligence Leaks and contains no contact information, accused Public Protector Thuli Madonsela of being a CIA spy. She has previously denied the allegations.

An opposition leader and a former opposition politician were also accused of working for American intelligence.

The State Security Agency, South Africa's intelligence service, said in a statement Thursday that it views the matter seriously because the allegations would undermine the "independence and credibility of our democratic institutions."