S Africa becoming powder keg: Tutu

South African Nobel laureate Desmond Tutu has used his 75th birthday to warn that the widening gap between rich and poor is turning South Africa into a powder keg that may explode into civil unrest.

The Anglican Archbishop was a key activist in ridding South Africa of apartheid but, at 75, his work is not over.

Now he is speaking on behalf of the poor blacks who make up the majority of the country's population.

"I am very surprised that it has taken them so long to vent their anger and their impatience," he said.

In the lead-up to his birthday, he has given a series of warnings about the country's moral weakness, blaming apartheid for damaging the population and now causing corruption and violent crime.