South Sudan conflict explained

Several countries are evacuating their citizens from South Sudan following days of fighting that have seen hundreds of people killed.

It follows a revival in the conflict between troops loyal to President Salva Kiir and Vice-President Riek Machar.

A civil war first broke out between the two groups in 2013. A peace deal was signed in August 2015.

So what are the causes of the civil war and reasons for the breakdown of the peace deal?