Clashes between armed rival groups in South Sudan are gradually turning into an all-out ethnic war between the two main tribes, Dinka and Nuer, as reports of mass killings based on ethnicity begin to emerge amid the ongoing bloody violence.

Witness reports from the capital Juba claim troops rounded up and shot more than 200 people, mostly from the Nuer ethnic group.

The UN says it has discovered a mass grave in the town of Bentiu, Unity State, containing about 75 bodies, with reports of two other mass graves in Juba.

South Sudan has been reeling under intensified violence in the past few days as rival army factions launch attacks against each other. President Salva Kiir, a Dinka, has been accusing dismissed opposition leader Riek Machar, who hails from the Nuer tribe, of attempting a coup against the government leading to the clashes, which are believed to have claimed at least 1,000 lives so far.

Meanwhile, UN Secretary General Ban Ki-moon has called for a sharp increase in the international troop presence in order to quell the spiralling violence.

Written by Alfred Joyner