Newly released US intelligence documents showed that the FBI continued to investigate South Africa's anti-apartheid icon Nelson Mandela as a potential "communist menace" even after his release from prison in 1990, a Washington-based group which sued to obtain the papers said.

Property of the People, which released the papers to mark 100 years since Mr Mandela's birth, said:

The documents reveal that, just as it did in the 1950s and 60s with Martin Luther King Jr and the civil rights movement, the FBI aggressively investigated the US and South African anti-apartheid movements as communist plots imperilling American security.

Worse still, the documents demonstrate the FBI continued its wrong-headed communist menace investigations of Mandela and the anti-apartheid movement even after US imposition of trade sanctions against apartheid South Africa, after Mandela's globally celebrated release from prison, and after the fall of the Berlin Wall."

Former US President Barack Obama gave a rousing speech in South Africa on Tuesday to celebrate Mr Mandela's life,calling on people to be inspired by him at a time when the "politics of fear, resentment, retrenchment" were rising.

Mr Mandela became South Africa's first black president in 1994, and advocated reconciliation with white people who had for decades enforced the racist system of apartheid in the country.

You can read more abut the documents by following the link on Property of the People's Twitter account.