Sebastião Salgado, regarded as one of the world's greatest documentary photographers, has died at the age of 81. The Brazil-born photographer was known for his dramatic and unflinching black-and-white images of hardship, conflict and natural beauty, captured in 130 countries over 55 years. His hard-hitting photos chronicled major global events such as the Rwanda genocide in 1994, burning oilfields at the end of the Gulf War in 1991, and the famine in the Sahel region of Africa in 1984.