Fighting between the armies of Uganda and neighbouring South Sudan, which are longtime allies, erupted this week over demarcations in disputed border regions, leading to the death of at least four soldiers, according to official reports from both sides. Thousands of civilians have since been displaced in affected areas as people fled to safety amid the rare outbreak of violence. A gunfight began on Monday and comes as South Sudan, one of the world’s youngest countries, is facing renewed violence due to fracturing within the government of President Salva Kiir that has led to fighting between South Sudanese troops and a rebel armed group. Uganda has been pivotal in keeping that issue contained by deploying troops to assist Kiir’s forces. However, the latest conflict between the two countries’ armies is raising questions regarding the state of that alliance. There are conflicting accounts of the events that began at about 4:25pm local time (13:25 GMT) on Monday, making it hard to pinpoint which side struck first. The two agree on where the fighting took place, but each claims the site as being in its own territory.

Full explanation : Disputes between the countries over border demarcations have been ongoing but heavy, armed fighting has been rare until now.