The two nations have been locked in a tense dispute over borders, territory and oil since the south split off and became its own country 18 months ago.

Negotiations between rebels and the government, now seem in danger of not happening, as both sides appear to be rearming.

Articles and multimedia in this series explore how the surge of poaching in Africa both feeds off and fuels instability on the continent.

Gunmen have killed four people and burned down a police station in northeast Adamawa State, a region where the militant Islamist sect Boko Haram is active, the police said.